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Walshe R, Pongsoipetch K, Mukem S, Kamsri T, Singkham N, Sudathip P, Kitchakarn S, Maude RR, Maude RJ. Assessing receptivity to malaria using case surveillance and forest data in a near-elimination setting in northeast Thailand. Malar J 2024; 23:224. [PMID: 39080748 PMCID: PMC11290226 DOI: 10.1186/s12936-024-05044-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Accepted: 07/16/2024] [Indexed: 08/02/2024] Open
Abstract
BACKGROUND Thailand aimed to eliminate malaria by 2024, and as such is planning for future prevention of re-establishment in malaria free provinces. Understanding the receptivity of local areas to malaria allows the appropriate targeting of interventions. Current approaches to assessing receptivity involve collecting entomological data. Forest coverage is known to be associated with malaria risk, as an environment conducive to both vector breeding and high-risk human behaviours. METHODS Geolocated, anonymized, individual-level surveillance data from 2011 to 2021 from the Thai Division of Vector-Borne Disease (DVBD) was used to calculate incidence and estimated Rc at village level. Forest cover was calculated using raster maps of tree crown cover density and year of forest loss from the publicly available Hansen dataset. Incidence and forest cover were compared graphically and using Spearman's rho. The current foci classification system was applied to data from the last 5 years (2017-2021) and forest cover for 2021 compared between the classifications. A simple risk score was developed to identify villages with high receptivity. RESULTS There was a non-linear decrease in annual cases by 96.6% (1061 to 36) across the two provinces from 2011 to 2021. Indigenous Annual Parasite Index (API) and approximated Rc were higher in villages in highly forested subdistricts, and with higher forest cover within 5 km. Forest cover was also higher in malaria foci which consistently reported malaria cases each year than those which did not. An Rc > 1 was only reported in villages in subdistricts with > 25% forest cover. When applying a simple risk score using forest cover and recent case history, the classifications were comparable to those of the risk stratification system currently used by the DVBD. CONCLUSIONS There was a positive association between forest coverage around a village and indigenous malaria cases. Most local transmission was observed in the heavily forested subdistricts on the international borders with Laos and Cambodia, which are where the most receptive villages are located. These areas are at greater risk of importation of malaria due to population mobility and forest-going activities. Combining forest cover and recent case surveillance data with measures of vulnerability may be useful for prediction of malaria recurrence risk.
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Affiliation(s)
- Rebecca Walshe
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
| | - Kulchada Pongsoipetch
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Suwanna Mukem
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Tanong Kamsri
- Phibun Mangsahan Hospital, Phibun, Ubon Ratchathani, Thailand
- Provincial Health Office, Ubon Ratchathani, Thailand
| | | | - Prayuth Sudathip
- Division of Vector Borne Diseases, Department of Disease Control, Tiwanond Road, Nonthaburi, 11000, Thailand
| | - Suravadee Kitchakarn
- Division of Vector Borne Diseases, Department of Disease Control, Tiwanond Road, Nonthaburi, 11000, Thailand
| | | | - Richard James Maude
- Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
- The Open University, Milton Keynes, UK.
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Guo B, Takala-Harrison S, O’Connor TD. Benchmarking and Optimization of Methods for the Detection of Identity-By-Descent in High-Recombining Plasmodium falciparum Genomes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.04.592538. [PMID: 38746392 PMCID: PMC11092787 DOI: 10.1101/2024.05.04.592538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Genomic surveillance is crucial for identifying at-risk populations for targeted malaria control and elimination. Identity-by-descent (IBD) is increasingly being used in Plasmodium population genomics to estimate genetic relatedness, effective population size (N e ), population structure, and signals of positive selection. Despite its potential, a thorough evaluation of IBD segment detection tools for species with high recombination rates, such as P. falciparum, remains absent. Here, we perform comprehensive benchmarking of IBD callers - probabilistic (hmmIBD, isoRelate), identity-by-state-based (hap-IBD, phased IBD) and others (Refined IBD) - using population genetic simulations tailored for high recombination, and IBD quality metrics at both the IBD segment level and the IBD-based downstream inference level. Our results demonstrate that low marker density per genetic unit, related to high recombination relative to mutation, significantly compromises the accuracy of detected IBD segments. In genomes with high recombination rates resembling P. falciparum, most IBD callers exhibit high false negative rates for shorter IBD segments, which can be partially mitigated through optimization of IBD caller parameters, especially those related to marker density. Notably, IBD detected with optimized parameters allows for more accurate capture of selection signals and population structure; IBD-based N e inference is very sensitive to IBD detection errors, with IBD called from hmmIBD uniquely providing less biased estimates of N e in this context. Validation with empirical data from the MalariaGEN Pf 7 database, representing different transmission settings, corroborates these findings. We conclude that context-specific evaluation and parameter optimization are essential for accurate IBD detection in high-recombining species and recommend hmmIBD for quality-sensitive analysis, such as estimation of N e in these species. Our optimization and high-level benchmarking methods not only improve IBD segment detection in high-recombining genomes but also enhance overall genomic analysis, paving the way for more accurate genomic surveillance and targeted intervention strategies for malaria.
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Affiliation(s)
- Bing Guo
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD USA
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Shannon Takala-Harrison
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD USA
| | - Timothy D. O’Connor
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
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3
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Davis EL, Crump RE, Medley GF, Solomon AW, Pemmaraju VRR, Hollingsworth TD. A modelling analysis of a new multi-stage pathway for classifying achievement of public health milestones for leprosy. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220408. [PMID: 37598707 PMCID: PMC10440169 DOI: 10.1098/rstb.2022.0408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 07/24/2023] [Indexed: 08/22/2023] Open
Abstract
Several countries have come close to eliminating leprosy, but leprosy cases continue to be detected at low levels. Due to the long, highly variable delay from infection to detection, the relationship between observed cases and transmission is uncertain. The World Health Organization's new technical guidance provides a path for countries to reach elimination. We use a simple probabilistic model to simulate the stochastic dynamics of detected cases as transmission declines, and evaluate progress through the new public health milestones. In simulations where transmission is halted, 5 years of zero incidence in autochthonous children, combined with 3 years of zero incidence in all ages is a flawed indicator that transmission has halted (54% correctly classified). A further 10 years of only occasional sporadic cases is associated with a high probability of having interrupted transmission (99%). If, however, transmission continues at extremely low levels, it is possible that cases could be misidentified as historic cases from the tail of the incubation period distribution, although misleadingly achieving all three milestones is unlikely (less than 1% probability across a 15-year period of ongoing low-level transmission). These results demonstrate the feasibility and challenges of a phased progression of milestones towards interruption of transmission, allowing assessment of programme status. This article is part of the theme issue 'Challenges and opportunities in the fight against neglected tropical diseases: a decade from the London Declaration on NTDs'.
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Affiliation(s)
- Emma L. Davis
- Mathematics Institute, University of Warwick, Coventry, CV4 7AL, UK
| | - Ron E. Crump
- Mathematics Institute, University of Warwick, Coventry, CV4 7AL, UK
| | - Graham F. Medley
- London School of Hygiene & Tropical Medicine, London, WC1E 7HT, UK
| | - Anthony W. Solomon
- Global Neglected Tropical Diseases Programme, World Health Organization, Geneva, 1211, Switzerland
| | | | - T. Déirdre Hollingsworth
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK
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4
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Parag KV, Obolski U. Risk averse reproduction numbers improve resurgence detection. PLoS Comput Biol 2023; 19:e1011332. [PMID: 37471464 PMCID: PMC10393178 DOI: 10.1371/journal.pcbi.1011332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Accepted: 07/06/2023] [Indexed: 07/22/2023] Open
Abstract
The effective reproduction number R is a prominent statistic for inferring the transmissibility of infectious diseases and effectiveness of interventions. R purportedly provides an easy-to-interpret threshold for deducing whether an epidemic will grow (R>1) or decline (R<1). We posit that this interpretation can be misleading and statistically overconfident when applied to infections accumulated from groups featuring heterogeneous dynamics. These groups may be delineated by geography, infectiousness or sociodemographic factors. In these settings, R implicitly weights the dynamics of the groups by their number of circulating infections. We find that this weighting can cause delayed detection of outbreak resurgence and premature signalling of epidemic control because it underrepresents the risks from highly transmissible groups. Applying E-optimal experimental design theory, we develop a weighting algorithm to minimise these issues, yielding the risk averse reproduction number E. Using simulations, analytic approaches and real-world COVID-19 data stratified at the city and district level, we show that E meaningfully summarises transmission dynamics across groups, balancing bias from the averaging underlying R with variance from directly using local group estimates. An E>1generates timely resurgence signals (upweighting risky groups), while an E<1ensures local outbreaks are under control. We propose E as an alternative to R for informing policy and assessing transmissibility at large scales (e.g., state-wide or nationally), where R is commonly computed but well-mixed or homogeneity assumptions break down.
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Affiliation(s)
- Kris V Parag
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
| | - Uri Obolski
- School of Public Health, Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Porter School of the Environment and Earth Sciences, Faculty of Exact Sciences, Tel Aviv University, Tel Aviv, Israel
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5
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Das AM, Hetzel MW, Yukich JO, Stuck L, Fakih BS, Al-Mafazy AWH, Ali A, Chitnis N. Modelling the impact of interventions on imported, introduced and indigenous malaria infections in Zanzibar, Tanzania. Nat Commun 2023; 14:2750. [PMID: 37173317 PMCID: PMC10182017 DOI: 10.1038/s41467-023-38379-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 04/26/2023] [Indexed: 05/15/2023] Open
Abstract
Malaria cases can be classified as imported, introduced or indigenous cases. The World Health Organization's definition of malaria elimination requires an area to demonstrate that no new indigenous cases have occurred in the last three years. Here, we present a stochastic metapopulation model of malaria transmission that distinguishes between imported, introduced and indigenous cases, and can be used to test the impact of new interventions in a setting with low transmission and ongoing case importation. We use human movement and malaria prevalence data from Zanzibar, Tanzania, to parameterise the model. We test increasing the coverage of interventions such as reactive case detection; implementing new interventions including reactive drug administration and treatment of infected travellers; and consider the potential impact of a reduction in transmission on Zanzibar and mainland Tanzania. We find that the majority of new cases on both major islands of Zanzibar are indigenous cases, despite high case importation rates. Combinations of interventions that increase the number of infections treated through reactive case detection or reactive drug administration can lead to substantial decreases in malaria incidence, but for elimination within the next 40 years, transmission reduction in both Zanzibar and mainland Tanzania is necessary.
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Affiliation(s)
- Aatreyee M Das
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland.
- University of Basel, Basel, Switzerland.
| | - Manuel W Hetzel
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
| | - Joshua O Yukich
- Center for Applied Malaria Research and Evaluation, Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA
| | - Logan Stuck
- Center for Applied Malaria Research and Evaluation, Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA
- Amsterdam Institute for Global Health and Development Amsterdam, Amsterdam, Netherlands
- Amsterdam University Medical Centers, Amsterdam, Netherlands
| | - Bakar S Fakih
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
- Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania
| | - Abdul-Wahid H Al-Mafazy
- Zanzibar Malaria Elimination Programme, Zanzibar, United Republic of Tanzania
- Office of the Chief Government Statistician (OCGS), Zanzibar, United Republic of Tanzania
| | - Abdullah Ali
- Zanzibar Malaria Elimination Programme, Zanzibar, United Republic of Tanzania
| | - Nakul Chitnis
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland.
- University of Basel, Basel, Switzerland.
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6
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Abdalal SA, Yukich J, Andrinopoulos K, Alghanmi M, Wakid MH, Zawawi A, Harakeh S, Altwaim SA, Gattan H, Baakdah F, Gaddoury MA, Niyazi HA, Mokhtar JA, Alruhaili MH, Alsaady I, Alhabbab R, Alfaleh M, Hashem AM, Alahmadey ZZ, Keating J. Livelihood activities, human mobility, and risk of malaria infection in elimination settings: a case-control study. Malar J 2023; 22:53. [PMID: 36782234 PMCID: PMC9926773 DOI: 10.1186/s12936-023-04470-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 01/24/2023] [Indexed: 02/15/2023] Open
Abstract
BACKGROUND Livelihood activities and human movements participate in the epidemiology of vector-borne diseases and influence malaria risk in elimination settings. In Saudi Arabia, where malaria transmission intensity varies geographically, it is vital to understand the components driving transmission within specific areas. In addition, shared social, behavioural, and occupational characteristics within communities may provoke the risk of malaria infection. This study aims to understand the relationship between human mobility, livelihood activities, and the risk of malaria infection in the border region of Jazan to facilitate further strategic malaria interventions. In addition, the study will complement and reinforce the existing efforts to eliminate malaria on the Saudi and Yemen border by providing a deeper understanding of human movement and livelihood activities. METHODS An unmatched case-control study was conducted. A total of 261 participants were recruited for the study, including 81 cases of confirmed malaria through rapid diagnostic tests (RDTs) and microscopy and 180 controls in the Baish Governorate in Jazan Provinces, Saudi Arabia. Individuals who received malaria tests were interviewed regarding their livelihood activities and recent movement (travel history). A questionnaire was administered, and the data was captured electronically. STATA software version 16 was used to analyse the data. Bivariate and multivariate analyses were conducted to determine if engaging in agricultural activities such as farming and animal husbandry, recent travel history outside of the home village within the last 30 days and participating in spiritual gatherings were related to malaria infection status. RESULTS A logistical regression model was used to investigate components associated with malaria infection. After adjusting several confounding factors, individuals who reported travelling away from their home village in the last 30 days OR 11.5 (95% CI 4.43-29.9), and those who attended a seasonal night spiritual gathering OR 3.04 (95% CI 1.10-8.42), involved in animal husbandry OR 2.52 (95% CI 1.10-5.82), and identified as male OR 4.57 (95% CI 1.43-14.7), were more likely to test positive for malaria infection. CONCLUSION Human movement and livelihood activities, especially at nighttime, should be considered malaria risk factors in malaria elimination settings, mainly when the targeted area is limited to a confined borderland area.
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Affiliation(s)
- Shaymaa A. Abdalal
- grid.412125.10000 0001 0619 1117Department of Medical Microbiology and Parasitology, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Joshua Yukich
- grid.265219.b0000 0001 2217 8588School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA USA
| | - Katherine Andrinopoulos
- grid.265219.b0000 0001 2217 8588School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA USA
| | - Maimonah Alghanmi
- grid.412125.10000 0001 0619 1117Vaccines and Immunotherapy Unit, King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia ,grid.412125.10000 0001 0619 1117Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Majed H. Wakid
- grid.412125.10000 0001 0619 1117Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia ,grid.412125.10000 0001 0619 1117Special Infectious Agents Unit, King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Ayat Zawawi
- grid.412125.10000 0001 0619 1117Vaccines and Immunotherapy Unit, King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia ,grid.412125.10000 0001 0619 1117Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Steve Harakeh
- grid.412125.10000 0001 0619 1117King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Sarah A. Altwaim
- grid.412125.10000 0001 0619 1117Department of Medical Microbiology and Parasitology, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia ,grid.412125.10000 0001 0619 1117Special Infectious Agents Unit, King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Hattan Gattan
- grid.412125.10000 0001 0619 1117Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia ,grid.412125.10000 0001 0619 1117Special Infectious Agents Unit, King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Fadi Baakdah
- grid.412125.10000 0001 0619 1117Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia ,grid.412125.10000 0001 0619 1117Special Infectious Agents Unit, King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Mahmoud A. Gaddoury
- grid.412125.10000 0001 0619 1117Department of Community Medicine, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Hatoon A. Niyazi
- grid.412125.10000 0001 0619 1117Department of Medical Microbiology and Parasitology, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Jawahir A. Mokhtar
- grid.412125.10000 0001 0619 1117Department of Medical Microbiology and Parasitology, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Mohammed H. Alruhaili
- grid.412125.10000 0001 0619 1117Department of Medical Microbiology and Parasitology, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia ,grid.412125.10000 0001 0619 1117Special Infectious Agents Unit, King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Isra Alsaady
- grid.412125.10000 0001 0619 1117Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia ,grid.412125.10000 0001 0619 1117Special Infectious Agents Unit, King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Rowa Alhabbab
- grid.412125.10000 0001 0619 1117Vaccines and Immunotherapy Unit, King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia ,grid.412125.10000 0001 0619 1117Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Mohamed Alfaleh
- grid.412125.10000 0001 0619 1117Vaccines and Immunotherapy Unit, King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia ,grid.412125.10000 0001 0619 1117Department of Pharmaceutics, Faculty of Pharmacy, King Abdulaziz University, Jeddah, 21589 Saudi Arabia
| | - Anwar M. Hashem
- grid.412125.10000 0001 0619 1117Department of Medical Microbiology and Parasitology, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia ,grid.412125.10000 0001 0619 1117Vaccines and Immunotherapy Unit, King Fahd Medical Research Centre, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Ziab Zakey Alahmadey
- grid.415696.90000 0004 0573 9824Microbiology and Serology Departments, Al-Ansar Hospital, Ministry of Health, Medina, Saudi Arabia
| | - Joseph Keating
- grid.265219.b0000 0001 2217 8588School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA USA
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Abdalal SA, Yukich J, Andrinoplous K, Harakeh S, Altwaim SA, Gattan H, Carter B, Shammaky M, Niyazi HA, Alruhaili MH, Keating J. An insight to better understanding cross border malaria in Saudi Arabia. Malar J 2023; 22:37. [PMID: 36732819 PMCID: PMC9893606 DOI: 10.1186/s12936-023-04467-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Accepted: 01/23/2023] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Border malaria is a major obstacle for the malaria elimination in Saudi Arabia. Today, the southern border of Saudi Arabia is a region where malaria cases are resurging, and malaria control is dwindling mainly due to the humanitarian crisis and the conflict in Yemen. This study analyses the current border malaria epidemiology along the southern border of Saudi Arabia from 2015 to 2018. METHODS All reported cases maintained by the malaria elimination centres in Aledabi and Baish, Jazan Province, Saudi Arabia, from 2015 to 2018 were analysed to examine the epidemiological changes over time. Pearson's Chi-Square test of differences was utilized to assess differences between the characteristics of imported and local causes and between border cases. A logistic regression model was used to predict imported status was related to living along side of the border area. RESULTS A total of 3210 malaria cases were reported in Baish and Aledabi malaria centres between 2015 and 2018, of which 170 were classified as local cases and 3040 were classified as imported cases. Reported malaria cases were mainly among males, within the imported cases 61.5% (1868/3039) were residents of the border areas. CONCLUSIONS Given the complexity of cross-border malaria, creating a malaria buffer zone that covers a certain margin from both sides of the border would allow for a joint force, cross-border malaria elimination programme. To initiate a malaria elimination activity and cases reported as belonging to this zone, rather than being pushed from one country to the other, would allow malaria elimination staff to work collaboratively with local borderland residents and other stakeholders to come up with innovative solutions to combat malaria and reach malaria-free borders.
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Affiliation(s)
- Shaymaa A. Abdalal
- grid.412126.20000 0004 0607 9688Department of Medical Microbiology and Parasitology, Faculty of Medicine, King Abdulaziz University and King Abdulaziz University Hospital, Jeddah, Saudi Arabia
| | - Joshua Yukich
- grid.265219.b0000 0001 2217 8588Tulane University School of Public Health and Tropical Medicine, New Orleans, LA USA
| | - Katherine Andrinoplous
- grid.265219.b0000 0001 2217 8588Tulane University School of Public Health and Tropical Medicine, New Orleans, LA USA
| | - Steve Harakeh
- Saudi Arabia Ministry of Health, Jazan, Saudi Arabia
| | - Sarah A. Altwaim
- grid.412126.20000 0004 0607 9688Department of Medical Microbiology and Parasitology, Faculty of Medicine, King Abdulaziz University and King Abdulaziz University Hospital, Jeddah, Saudi Arabia
| | - Hattan Gattan
- grid.412125.10000 0001 0619 1117Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Brendan Carter
- grid.265219.b0000 0001 2217 8588Tulane University School of Public Health and Tropical Medicine, New Orleans, LA USA
| | | | - Hatoon A. Niyazi
- grid.412126.20000 0004 0607 9688Department of Medical Microbiology and Parasitology, Faculty of Medicine, King Abdulaziz University and King Abdulaziz University Hospital, Jeddah, Saudi Arabia
| | - Mohammed H. Alruhaili
- grid.412126.20000 0004 0607 9688Department of Medical Microbiology and Parasitology, Faculty of Medicine, King Abdulaziz University and King Abdulaziz University Hospital, Jeddah, Saudi Arabia
| | - Joseph Keating
- grid.265219.b0000 0001 2217 8588Tulane University School of Public Health and Tropical Medicine, New Orleans, LA USA
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Das AM, Hetzel MW, Yukich JO, Stuck L, Fakih BS, Al-Mafazy AWH, Ali A, Chitnis N. The impact of reactive case detection on malaria transmission in Zanzibar in the presence of human mobility. Epidemics 2022; 41:100639. [PMID: 36343496 PMCID: PMC9758615 DOI: 10.1016/j.epidem.2022.100639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 09/02/2022] [Accepted: 10/03/2022] [Indexed: 12/29/2022] Open
Abstract
Malaria persists at low levels on Zanzibar despite the use of vector control and case management. We use a metapopulation model to investigate the role of human mobility in malaria persistence on Zanzibar, and the impact of reactive case detection. The model was parameterized using survey data on malaria prevalence, reactive case detection, and travel history. We find that in the absence of imported cases from mainland Tanzania, malaria would likely cease to persist on Zanzibar. We also investigate potential intervention scenarios that may lead to elimination, especially through changes to reactive case detection. While we find that some additional cases are removed by reactive case detection, a large proportion of cases are missed due to many infections having a low parasite density that go undetected by rapid diagnostic tests, a low rate of those infected with malaria seeking treatment, and a low rate of follow up at the household level of malaria cases detected at health facilities. While improvements in reactive case detection would lead to a reduction in malaria prevalence, none of the intervention scenarios tested here were sufficient to reach elimination. Imported cases need to be treated to have a substantial impact on prevalence.
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Affiliation(s)
- Aatreyee M Das
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland; University of Basel, Basel, Switzerland.
| | - Manuel W Hetzel
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland; University of Basel, Basel, Switzerland
| | - Joshua O Yukich
- Center for Applied Malaria Research and Evaluation, Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA
| | - Logan Stuck
- Center for Applied Malaria Research and Evaluation, Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA, USA
| | - Bakar S Fakih
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland; University of Basel, Basel, Switzerland; Ifakara Health Institute, Dar es Salaam, United Republic of Tanzania
| | | | - Abdullah Ali
- Zanzibar Malaria Elimination Programme, Zanzibar, United Republic of Tanzania
| | - Nakul Chitnis
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland; University of Basel, Basel, Switzerland
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Zhang Y, Britton T, Zhou X. Monitoring real-time transmission heterogeneity from incidence data. PLoS Comput Biol 2022; 18:e1010078. [PMID: 36455043 PMCID: PMC9746975 DOI: 10.1371/journal.pcbi.1010078] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 12/13/2022] [Accepted: 11/16/2022] [Indexed: 12/03/2022] Open
Abstract
The transmission heterogeneity of an epidemic is associated with a complex mixture of host, pathogen and environmental factors. And it may indicate superspreading events to reduce the efficiency of population-level control measures and to sustain the epidemic over a larger scale and a longer duration. Methods have been proposed to identify significant transmission heterogeneity in historic epidemics based on several data sources, such as contact history, viral genomes and spatial information, which may not be available, and more importantly ignore the temporal trend of transmission heterogeneity. Here we attempted to establish a convenient method to estimate real-time heterogeneity over an epidemic. Within the branching process framework, we introduced an instant-individualheterogenous infectiousness model to jointly characterize the variation in infectiousness both between individuals and among different times. With this model, we could simultaneously estimate the transmission heterogeneity and the reproduction number from incidence time series. We validated the model with data of both simulated and real outbreaks. Our estimates of the overall and real-time heterogeneities of the six epidemics were consistent with those presented in the literature. Additionally, our model is robust to the ubiquitous bias of under-reporting and misspecification of serial interval. By analyzing recent data from South Africa, we found evidence that the Omicron might be of more significant transmission heterogeneity than Delta. Our model based on incidence data was proved to be reliable in estimating the real-time transmission heterogeneity.
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Affiliation(s)
- Yunjun Zhang
- Department of Biostatistics, School of Public Health, Peking University, Beijing, China
- Center for Statistical Science, Peking University, Beijing, China
| | - Tom Britton
- Department of Mathematics, Stockholm University, Stockholm, Sweden
| | - Xiaohua Zhou
- Department of Biostatistics, School of Public Health, Peking University, Beijing, China
- Center for Statistical Science, Peking University, Beijing, China
- Beijing International Center for Mathematical Research, Peking University, Beijing, China
- School of Mathematical Sciences, Peking University, Beijing, China
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10
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Gautam R, Pokharel A, Adhikari K, Uprety KN, Vaidya NK. Modeling malaria transmission in Nepal: impact of imported cases through cross-border mobility. JOURNAL OF BIOLOGICAL DYNAMICS 2022; 16:528-564. [PMID: 35833562 DOI: 10.1080/17513758.2022.2096935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 06/24/2022] [Indexed: 06/15/2023]
Abstract
The cross-border mobility of malaria cases poses an obstacle to malaria elimination programmes in many countries, including Nepal. Here, we develop a novel mathematical model to study how the imported malaria cases through the Nepal-India open-border affect the Nepal government's goal of eliminating malaria by 2026. Mathematical analyses and numerical simulations of our model, validated by malaria case data from Nepal, indicate that eliminating malaria from Nepal is possible if strategies promoting the absence of cross-border mobility, complete protection of transmission abroad, or strict border screening and isolation are implemented. For each strategy, we establish the conditions for the elimination of malaria. We further use our model to identify the control strategies that can help maintain a low endemic level. Our results show that the ideal control strategies should be designed according to the average mosquito biting rates that may depend on the location and season.
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Affiliation(s)
- Ramesh Gautam
- Ratna Rajya Laxmi Campus, Tribhuvan University, KTM, Nepal
| | - Anjana Pokharel
- Padma Kanya Multiple Campus, Tribhuvan University, KTM, Nepal
| | | | | | - Naveen K Vaidya
- Department of Mathematics and Statistics, San Diego State University, San Diego, CA, USA
- Computational Science Research Center, San Diego State University, San Diego, CA, USA
- Viral Information Institute, San Diego State University, San Diego, CA, USA
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11
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Stresman G, DePina AJ, Nelli L, Monteiro DDS, Leal SDV, Moreira AL, Furtado UD, Roka JCL, Neatherlin J, Gomes C, Tfeil AK, Lindblade KA. Factors related to human-vector contact that modify the likelihood of malaria transmission during a contained Plasmodium falciparum outbreak in Praia, Cabo Verde. FRONTIERS IN EPIDEMIOLOGY 2022; 2:1031230. [PMID: 38455281 PMCID: PMC10910924 DOI: 10.3389/fepid.2022.1031230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 11/10/2022] [Indexed: 03/09/2024]
Abstract
Background Determining the reproductive rate and how it varies over time and space (RT) provides important insight to understand transmission of a given disease and inform optimal strategies for controlling or eliminating it. Estimating RT for malaria is difficult partly due to the widespread use of interventions and immunity to disease masking incident infections. A malaria outbreak in Praia, Cabo Verde in 2017 provided a unique opportunity to estimate RT directly, providing a proxy for the intensity of vector-human contact and measure the impact of vector control measures. Methods Out of 442 confirmed malaria cases reported in 2017 in Praia, 321 (73%) were geolocated and informed this analysis. RT was calculated using the joint likelihood of transmission between two cases, based on the time (serial interval) and physical distance (spatial interval) between them. Log-linear regression was used to estimate factors associated with changes in RT, including the impact of vector control interventions. A geostatistical model was developed to highlight areas receptive to transmission where vector control activities could be focused in future to prevent or interrupt transmission. Results The RT from individual cases ranged between 0 and 11 with a median serial- and spatial-interval of 34 days [interquartile range (IQR): 17-52] and 1,347 m (IQR: 832-1,985 m), respectively. The number of households receiving indoor residual spraying (IRS) 4 weeks prior was associated with a reduction in RT by 0.84 [95% confidence interval (CI) 0.80-0.89; p-value <0.001] in the peak-and post-epidemic compared to the pre-epidemic period. Conclusions Identifying the effect of reduced human-vector contact through IRS is essential to determining optimal intervention strategies that modify the likelihood of malaria transmission and can inform optimal intervention strategies to accelerate time to elimination. The distance within which two cases are plausibly linked is important for the potential scale of any reactive interventions as well as classifying infections as imported or introduced and confirming malaria elimination.
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Affiliation(s)
- Gillian Stresman
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom
- College of Public Health, University of South Florida, Tampa, FL, United States
| | | | - Luca Nelli
- School of Biodiversity, One Health, and Veterinary Medicine, University of Glasgow, Glasgow, United Kingdom
| | | | - Silvânia da Veiga Leal
- Laboratório de Entomologia Médica, Instituto Nacional de Saúde Pública, Praia, Cabo Verde
| | | | | | | | - John Neatherlin
- U.S. Centers for Disease Control and Prevention, Atlanta, GA, United States
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12
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Parag KV, Donnelly CA, Zarebski AE. Quantifying the information in noisy epidemic curves. NATURE COMPUTATIONAL SCIENCE 2022; 2:584-594. [PMID: 38177483 DOI: 10.1038/s43588-022-00313-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 08/08/2022] [Indexed: 01/06/2024]
Abstract
Reliably estimating the dynamics of transmissible diseases from noisy surveillance data is an enduring problem in modern epidemiology. Key parameters are often inferred from incident time series, with the aim of informing policy-makers on the growth rate of outbreaks or testing hypotheses about the effectiveness of public health interventions. However, the reliability of these inferences depends critically on reporting errors and latencies innate to the time series. Here, we develop an analytical framework to quantify the uncertainty induced by under-reporting and delays in reporting infections, as well as a metric for ranking surveillance data informativeness. We apply this metric to two primary data sources for inferring the instantaneous reproduction number: epidemic case and death curves. We find that the assumption of death curves as more reliable, commonly made for acute infectious diseases such as COVID-19 and influenza, is not obvious and possibly untrue in many settings. Our framework clarifies and quantifies how actionable information about pathogen transmissibility is lost due to surveillance limitations.
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Affiliation(s)
- Kris V Parag
- NIHR Health Protection Research Unit in Behavioural Science and Evaluation, University of Bristol, Bristol, UK.
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK.
| | - Christl A Donnelly
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
- Department of Statistics, University of Oxford, Oxford, UK
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13
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Fahmi F, Pasaribu AP, Theodora M, Wangdi K. Spatial analysis to evaluate risk of malaria in Northern Sumatera, Indonesia. Malar J 2022; 21:241. [PMID: 35987665 PMCID: PMC9392258 DOI: 10.1186/s12936-022-04262-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 08/11/2022] [Indexed: 12/02/2022] Open
Abstract
Background As Indonesia aims for malaria elimination by 2030, provisional malaria epidemiology and risk factors evaluation are important in pursue of this national goal. Therefore, this study aimed to understand the risk factor of malaria in Northern Sumatera. Methods Malaria cases from 2019 to 2020 were obtained from the Indonesian Ministry of Health Electronic Database. Climatic variables were provided by the Center for Meteorology and Geophysics Medan branch office. Multivariable logistic regression was undertaken to understand the risk factors of imported malaria. A zero-inflated Poisson multivariable regression model was used to study the climatic drivers of indigenous malaria. Results A total of 2208 (indigenous: 76.0% [1679] and imported: 17.8% [392]) were reported during the study period. Risk factors of imported malaria were: ages 19–30 (adjusted odds ratio [AOR] = 3.31; 95% confidence interval [CI] 1.67, 2.56), 31–45 (AOR = 5.69; 95% CI 2.65, 12.20), and > 45 years (AOR = 5.11; 95% CI 2.41, 10.84). Military personnel and forest workers and miners were 1,154 times (AOR = 197.03; 95% CI 145.93, 9,131.56) and 44 times (AOR = 44.16; 95% CI 4.08, 477,93) more likely to be imported cases as compared to those working as employees and traders. Indigenous Plasmodium falciparum increased by 12.1% (95% CrI 5.1%, 20.1%) for 1% increase in relative humidity and by 21.0% (95% CrI 9.0%, 36.2%) for 1 °C increase in maximum temperature. Plasmodium vivax decreased by 0.8% (95% CrI 0.2%, 1.3%) and 16.7% (95% CrI 13.7%, 19.9%) for one meter and 1 °C increase of altitude and minimum temperature. Indigenous hotspot was reported by Kota Tanjung Balai city and Asahan regency, respectively. Imported malaria hotspots were reported in Batu Bara, Kota Tebing Tinggi, Serdang Bedagai and Simalungun. Conclusion Both indigenous and imported malaria is limited to a few regencies and cities in Northern Sumatera. The control measures should focus on these risk factors to achieve elimination in Indonesia. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-022-04262-y.
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Dlamini SN, Fall IS, Mabaso SD. Bayesian Geostatistical Modeling to Assess Malaria Seasonality and Monthly Incidence Risk in Eswatini. J Epidemiol Glob Health 2022; 12:340-361. [PMID: 35976542 PMCID: PMC9382628 DOI: 10.1007/s44197-022-00054-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 08/06/2022] [Indexed: 11/30/2022] Open
Abstract
Eswatini is on the brink of malaria elimination and had however, had to shift its target year to eliminate malaria on several occasions since 2015 as the country struggled to achieve its zero malaria goal. We conducted a Bayesian geostatistical modeling study using malaria case data. A Bayesian distributed lags model (DLM) was implemented to assess the effects of seasonality on cases. A second Bayesian model based on polynomial distributed lags was implemented on the dataset to improve understanding of the lag effect of environmental factors on cases. Results showed that malaria increased during the dry season with proportion 0.051 compared to the rainy season with proportion 0.047 while rainfall of the preceding month (Lag2) had negative effect on malaria as it decreased by proportion − 0.25 (BCI: − 0.46, − 0.05). Night temperatures of the preceding first and second month were significantly associated with increased malaria in the following proportions: at Lag1 0.53 (BCI: 0.23, 0.84) and at Lag2 0.26 (BCI: 0.01, 0.51). Seasonality was an important predictor of malaria with proportion 0.72 (BCI: 0.40, 0.98). High malaria rates were identified for the months of July to October, moderate rates in the months of November to February and low rates in the months of March to June. The maps produced support-targeted malaria control interventions. The Bayesian geostatistical models could be extended for short-term and long-term forecasting of malaria supporting-targeted response both in space and time for effective elimination.
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Affiliation(s)
- Sabelo Nick Dlamini
- Department of Geography, University of Eswatini, Kwaluseni, Manzini, M200, Eswatini. .,World Health Organization, 27 Geneva, Geneva, Switzerland.
| | | | - Sizwe Doctor Mabaso
- Department of Geography, University of Eswatini, Kwaluseni, Manzini, M200, Eswatini
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15
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Yukich JO, Lindblade K, Kolaczinski J. Receptivity to malaria: meaning and measurement. Malar J 2022; 21:145. [PMID: 35527264 PMCID: PMC9080212 DOI: 10.1186/s12936-022-04155-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Accepted: 04/07/2022] [Indexed: 01/13/2023] Open
Abstract
"Receptivity" to malaria is a construct developed during the Global Malaria Eradication Programme (GMEP) era. It has been defined in varied ways and no consistent, quantitative definition has emerged over the intervening decades. Despite the lack of consistency in defining this construct, the idea that some areas are more likely to sustain malaria transmission than others has remained important in decision-making in malaria control, planning for malaria elimination and guiding activities during the prevention of re-establishment (POR) period. This manuscript examines current advances in methods of measurement. In the context of a decades long decline in global malaria transmission and an increasing number of countries seeking to eliminate malaria, understanding and measuring malaria receptivity has acquired new relevance.
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Affiliation(s)
- Joshua O. Yukich
- grid.265219.b0000 0001 2217 8588Department of Tropical Medicine, Center for Applied Malaria Research and Evaluation, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA USA
| | - Kim Lindblade
- grid.3575.40000000121633745Global Malaria Programme, World Health Organization, Geneva, CH USA
| | - Jan Kolaczinski
- grid.3575.40000000121633745Global Malaria Programme, World Health Organization, Geneva, CH USA
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16
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Huber JH, Hsiang MS, Dlamini N, Murphy M, Vilakati S, Nhlabathi N, Lerch A, Nielsen R, Ntshalintshali N, Greenhouse B, Perkins TA. Inferring person-to-person networks of Plasmodium falciparum transmission: are analyses of routine surveillance data up to the task? Malar J 2022; 21:58. [PMID: 35189905 PMCID: PMC8860266 DOI: 10.1186/s12936-022-04072-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Accepted: 01/31/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Inference of person-to-person transmission networks using surveillance data is increasingly used to estimate spatiotemporal patterns of pathogen transmission. Several data types can be used to inform transmission network inferences, yet the sensitivity of those inferences to different data types is not routinely evaluated. METHODS The influence of different combinations of spatial, temporal, and travel-history data on transmission network inferences for Plasmodium falciparum malaria were evaluated. RESULTS The information content of these data types may be limited for inferring person-to-person transmission networks and may lead to an overestimate of transmission. Only when outbreaks were temporally focal or travel histories were accurate was the algorithm able to accurately estimate the reproduction number under control, Rc. Applying this approach to data from Eswatini indicated that inferences of Rc and spatiotemporal patterns therein depend upon the choice of data types and assumptions about travel-history data. CONCLUSIONS These results suggest that transmission network inferences made with routine malaria surveillance data should be interpreted with caution.
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Affiliation(s)
- John H Huber
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA.
| | - Michelle S Hsiang
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Malaria Elimination Initiative, Global Health Group, University of California, San Francisco, CA, USA.,Department of Pediatrics, University of California, San Francisco,, CA, USA
| | - Nomcebo Dlamini
- National Malaria Elimination Programme, Ministry of Health, Manzini, Eswatini
| | - Maxwell Murphy
- Department of Medicine, University of California, San Francisco, CA, USA
| | | | - Nomcebo Nhlabathi
- National Malaria Elimination Programme, Ministry of Health, Manzini, Eswatini
| | - Anita Lerch
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Rasmus Nielsen
- Department of Integrative Biology and Statistics, University of California, Berkeley, CA, USA
| | | | - Bryan Greenhouse
- Department of Medicine, University of California, San Francisco, CA, USA.,Chan Zuckerberg Biohub, San Francisco, CA, USA
| | - T Alex Perkins
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA.
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Champagne C, Gerhards M, Lana J, García Espinosa B, Bradley C, González O, Cohen JM, Le Menach A, White MT, Pothin E. Using observed incidence to calibrate the transmission level of a mathematical model for Plasmodium vivax dynamics including case management and importation. Math Biosci 2021; 343:108750. [PMID: 34883106 PMCID: PMC8786669 DOI: 10.1016/j.mbs.2021.108750] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 10/29/2021] [Accepted: 10/29/2021] [Indexed: 11/27/2022]
Abstract
In this work, we present a simple and flexible model for Plasmodium vivax dynamics which can be easily combined with routinely collected data on local and imported case counts to quantify transmission intensity and simulate control strategies. This model extends the model from White et al. (2016) by including case management interventions targeting liver-stage or blood-stage parasites, as well as imported infections. The endemic steady state of the model is used to derive a relationship between the observed incidence and the transmission rate in order to calculate reproduction numbers and simulate intervention scenarios. To illustrate its potential applications, the model is used to calculate local reproduction numbers in Panama and identify areas of sustained malaria transmission that should be targeted by control interventions.
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Affiliation(s)
- Clara Champagne
- Swiss Tropical and Public Health Institute, Socinstrasse 57, P.O. Box, Basel, CH-4002, Switzerland; University of Basel, Petersplatz 1, P.O. Box, Basel, CH-4001, Switzerland.
| | - Maximilian Gerhards
- Swiss Tropical and Public Health Institute, Socinstrasse 57, P.O. Box, Basel, CH-4002, Switzerland; University of Basel, Petersplatz 1, P.O. Box, Basel, CH-4001, Switzerland
| | - Justin Lana
- Clinton Health Access Initiative, 383 Dorchester Ave, Suite 400, Boston, 02127, MA, USA
| | | | - Christina Bradley
- Clinton Health Access Initiative, 383 Dorchester Ave, Suite 400, Boston, 02127, MA, USA
| | - Oscar González
- Ministerio de Salud de Panama, Calle culebra, Edificio 265 del Ministerio de Salud, Corregimiento de Ancón, Panama
| | - Justin M Cohen
- Clinton Health Access Initiative, 383 Dorchester Ave, Suite 400, Boston, 02127, MA, USA
| | - Arnaud Le Menach
- Clinton Health Access Initiative, 383 Dorchester Ave, Suite 400, Boston, 02127, MA, USA
| | - Michael T White
- Institut Pasteur, Université de Paris, G5 Épidémiologie et Analyse des Maladies Infectieuses, Département de Santé Globale, Paris, F-75015, France
| | - Emilie Pothin
- Swiss Tropical and Public Health Institute, Socinstrasse 57, P.O. Box, Basel, CH-4002, Switzerland; University of Basel, Petersplatz 1, P.O. Box, Basel, CH-4001, Switzerland; Clinton Health Access Initiative, 383 Dorchester Ave, Suite 400, Boston, 02127, MA, USA
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18
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Metcalf CJE, Andriamandimby SF, Baker RE, Glennon EE, Hampson K, Hollingsworth TD, Klepac P, Wesolowski A. Challenges in evaluating risks and policy options around endemic establishment or elimination of novel pathogens. Epidemics 2021; 37:100507. [PMID: 34823222 PMCID: PMC7612525 DOI: 10.1016/j.epidem.2021.100507] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 08/20/2021] [Accepted: 10/06/2021] [Indexed: 11/12/2022] Open
Abstract
When a novel pathogen emerges there may be opportunities to eliminate transmission - locally or globally - whilst case numbers are low. However, the effort required to push a disease to elimination may come at a vast cost at a time when uncertainty is high. Models currently inform policy discussions on this question, but there are a number of open challenges, particularly given unknown aspects of the pathogen biology, the effectiveness and feasibility of interventions, and the intersecting political, economic, sociological and behavioural complexities for a novel pathogen. In this overview, we detail how models might identify directions for better leveraging or expanding the scope of data available on the pathogen trajectory, for bounding the theoretical context of emergence relative to prospects for elimination, and for framing the larger economic, behavioural and social context that will influence policy decisions and the pathogen’s outcome.
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Affiliation(s)
- C Jessica E Metcalf
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA; Princeton School of Public and International Affairs, Princeton University, Princeton, USA.
| | | | - Rachel E Baker
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA; Princeton High Meadows Environmental Institute, Princeton University, Princeton, NJ, USA
| | - Emma E Glennon
- Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, UK
| | - Katie Hampson
- Institute of Biodiversity, Animal Health & Comparative Medicine, University of Glasgow, Glasgow, UK
| | - T Deirdre Hollingsworth
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, UK
| | - Petra Klepac
- London School of Hygiene and Tropical Medicine, London, UK
| | - Amy Wesolowski
- Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA
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19
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Parag KV. Improved estimation of time-varying reproduction numbers at low case incidence and between epidemic waves. PLoS Comput Biol 2021; 17:e1009347. [PMID: 34492011 PMCID: PMC8448340 DOI: 10.1371/journal.pcbi.1009347] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 09/17/2021] [Accepted: 08/13/2021] [Indexed: 12/15/2022] Open
Abstract
We construct a recursive Bayesian smoother, termed EpiFilter, for estimating the effective reproduction number, R, from the incidence of an infectious disease in real time and retrospectively. Our approach borrows from Kalman filtering theory, is quick and easy to compute, generalisable, deterministic and unlike many current methods, requires no change-point or window size assumptions. We model R as a flexible, hidden Markov state process and exactly solve forward-backward algorithms, to derive R estimates that incorporate all available incidence information. This unifies and extends two popular methods, EpiEstim, which considers past incidence, and the Wallinga-Teunis method, which looks forward in time. We find that this combination of maximising information and minimising assumptions significantly reduces the bias and variance of R estimates. Moreover, these properties make EpiFilter more statistically robust in periods of low incidence, where several existing methods can become destabilised. As a result, EpiFilter offers improved inference of time-varying transmission patterns that are advantageous for assessing the risk of upcoming waves of infection or the influence of interventions, in real time and at various spatial scales.
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Affiliation(s)
- Kris V. Parag
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
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20
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Parag KV. Improved estimation of time-varying reproduction numbers at low case incidence and between epidemic waves. PLoS Comput Biol 2021. [PMID: 34492011 DOI: 10.1101/2020.09.14.20194589v1.abstract] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/15/2023] Open
Abstract
We construct a recursive Bayesian smoother, termed EpiFilter, for estimating the effective reproduction number, R, from the incidence of an infectious disease in real time and retrospectively. Our approach borrows from Kalman filtering theory, is quick and easy to compute, generalisable, deterministic and unlike many current methods, requires no change-point or window size assumptions. We model R as a flexible, hidden Markov state process and exactly solve forward-backward algorithms, to derive R estimates that incorporate all available incidence information. This unifies and extends two popular methods, EpiEstim, which considers past incidence, and the Wallinga-Teunis method, which looks forward in time. We find that this combination of maximising information and minimising assumptions significantly reduces the bias and variance of R estimates. Moreover, these properties make EpiFilter more statistically robust in periods of low incidence, where several existing methods can become destabilised. As a result, EpiFilter offers improved inference of time-varying transmission patterns that are advantageous for assessing the risk of upcoming waves of infection or the influence of interventions, in real time and at various spatial scales.
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Affiliation(s)
- Kris V Parag
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
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21
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Abstract
We show that sub-spreading events, i.e. transmission events in which an infection propagates to few or no individuals, can be surprisingly important for defining the lifetime of an infectious disease epidemic and hence its waiting time to elimination or fade-out, measured from the time-point of its last observed case. While limiting super-spreading promotes more effective control when cases are growing, we find that when incidence is waning, curbing sub-spreading is more important for achieving reliable elimination of the epidemic. Controlling super-spreading in this low-transmissibility phase offers diminishing returns over non-selective, population-wide measures. By restricting sub-spreading, we efficiently dampen remaining variations among the reproduction numbers of infectious events, which minimizes the risk of premature and late end-of-epidemic declarations. Because case-ascertainment or reporting rates can be modelled in exactly the same way as control policies, we concurrently show that the under-reporting of sub-spreading events during waning phases will engender overconfident assessments of epidemic elimination. While controlling sub-spreading may not be easily realized, the likely neglecting of these events by surveillance systems could result in unexpectedly risky end-of-epidemic declarations. Super-spreading controls the size of the epidemic peak but sub-spreading mediates the variability of its tail.
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Affiliation(s)
- Kris V Parag
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London W2 1PG, UK
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22
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Zhao S, Musa SS, Meng J, Qin J, He D. The long-term changing dynamics of dengue infectivity in Guangdong, China, from 2008-2018: a modelling analysis. Trans R Soc Trop Med Hyg 2021; 114:62-71. [PMID: 31638154 DOI: 10.1093/trstmh/trz084] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 07/02/2019] [Accepted: 07/19/2019] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Dengue remains a severe threat to public health in tropical and subtropical regions. In China, over 85% of domestic dengue cases are in the Guangdong province and there were 53 139 reported cases during 2008-2018. In Guangdong, the 2014 dengue outbreak was the largest in the last 20 y and it was probably triggered by a new strain imported from other regions. METHODS We studied the long-term patterns of dengue infectivity in Guangdong from 2008-2018 and compared the infectivity estimates across different periods. RESULTS We found that the annual epidemics approximately followed exponential growth during 2011-2014. The transmission rates were at a low level during 2008-2012, significantly increased 1.43-fold [1.22, 1.69] during 2013-2014 and then decreased back to a low level after 2015. By using the mosquito index and the likelihood-inference approach, we found that the new strain most likely invaded Guangdong in April 2014. CONCLUSIONS The long-term changing dynamics of dengue infectivity are associated with the new dengue virus strain invasion and public health control programmes. The increase in infectiousness indicates the potential for dengue to go from being imported to becoming an endemic in Guangdong, China.
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Affiliation(s)
- Shi Zhao
- School of Nursing, Hong Kong Polytechnic University, Hong Kong, China.,Department of Applied Mathematics, Hong Kong Polytechnic University, Hong Kong, China
| | - Salihu S Musa
- Department of Applied Mathematics, Hong Kong Polytechnic University, Hong Kong, China
| | - Jiayi Meng
- School of Economics and Finance, Xi'an International Studies University, Xi'an, China
| | - Jing Qin
- School of Nursing, Hong Kong Polytechnic University, Hong Kong, China
| | - Daihai He
- Department of Applied Mathematics, Hong Kong Polytechnic University, Hong Kong, China
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23
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Sun H, Dickens BL, Jit M, Cook AR, Carrasco LR. Mapping the cryptic spread of the 2015-2016 global Zika virus epidemic. BMC Med 2020; 18:399. [PMID: 33327961 PMCID: PMC7744256 DOI: 10.1186/s12916-020-01845-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 11/06/2020] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND Zika virus (ZIKV) emerged as a global epidemic in 2015-2016 from Latin America with its true geographical extent remaining unclear due to widely presumed underreporting. The identification of locations with potential and unknown spread of ZIKV is a key yet understudied component for outbreak preparedness. Here, we aim to identify locations at a high risk of cryptic ZIKV spread during 2015-2016 to further the understanding of the global ZIKV epidemiology, which is critical for the mitigation of the risk of future epidemics. METHODS We developed an importation simulation model to estimate the weekly number of ZIKV infections imported in each susceptible spatial unit (i.e. location that did not report any autochthonous Zika cases during 2015-2016), integrating epidemiological, demographic, and travel data as model inputs. Thereafter, a global risk model was applied to estimate the weekly ZIKV transmissibility during 2015-2016 for each location. Finally, we assessed the risk of onward ZIKV spread following importation in each susceptible spatial unit to identify locations with a high potential for cryptic ZIKV spread during 2015-2016. RESULTS We have found 24 susceptible spatial units that were likely to have experienced cryptic ZIKV spread during 2015-2016, of which 10 continue to have a high risk estimate within a highly conservative scenario, namely, Luanda in Angola, Banten in Indonesia, Maharashtra in India, Lagos in Nigeria, Taiwan and Guangdong in China, Dakar in Senegal, Maputo in Mozambique, Kinshasa in Congo DRC, and Pool in Congo. Notably, among the 24 susceptible spatial units identified, some have reported their first ZIKV outbreaks since 2017, thus adding to the credibility of our results (derived using 2015-2016 data only). CONCLUSION Our study has provided valuable insights into the potentially high-risk locations for cryptic ZIKV circulation during the 2015-2016 pandemic and has also laid a foundation for future studies that attempt to further narrow this key knowledge gap. Our modelling framework can be adapted to identify areas with likely unknown spread of other emerging vector-borne diseases, which has important implications for public health readiness especially in resource-limited settings.
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Affiliation(s)
- Haoyang Sun
- Saw Swee Hock School of Public Health, National University of Singapore, 12 Science Drive 2, Singapore, 117549, Republic of Singapore.
| | - Borame L Dickens
- Saw Swee Hock School of Public Health, National University of Singapore, 12 Science Drive 2, Singapore, 117549, Republic of Singapore
| | - Mark Jit
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
- Modelling and Economics Unit, Public Health England, London, UK
| | - Alex R Cook
- Saw Swee Hock School of Public Health, National University of Singapore, 12 Science Drive 2, Singapore, 117549, Republic of Singapore.
| | - L Roman Carrasco
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore, 117543, Republic of Singapore
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24
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Parag KV, Donnelly CA, Jha R, Thompson RN. An exact method for quantifying the reliability of end-of-epidemic declarations in real time. PLoS Comput Biol 2020; 16:e1008478. [PMID: 33253158 PMCID: PMC7717584 DOI: 10.1371/journal.pcbi.1008478] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 12/04/2020] [Accepted: 10/28/2020] [Indexed: 12/13/2022] Open
Abstract
We derive and validate a novel and analytic method for estimating the probability that an epidemic has been eliminated (i.e. that no future local cases will emerge) in real time. When this probability crosses 0.95 an outbreak can be declared over with 95% confidence. Our method is easy to compute, only requires knowledge of the incidence curve and the serial interval distribution, and evaluates the statistical lifetime of the outbreak of interest. Using this approach, we show how the time-varying under-reporting of infected cases will artificially inflate the inferred probability of elimination, leading to premature (false-positive) end-of-epidemic declarations. Contrastingly, we prove that incorrectly identifying imported cases as local will deceptively decrease this probability, resulting in delayed (false-negative) declarations. Failing to sustain intensive surveillance during the later phases of an epidemic can therefore substantially mislead policymakers on when it is safe to remove travel bans or relax quarantine and social distancing advisories. World Health Organisation guidelines recommend fixed (though disease-specific) waiting times for end-of-epidemic declarations that cannot accommodate these variations. Consequently, there is an unequivocal need for more active and specialised metrics for reliably identifying the conclusion of an epidemic.
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Affiliation(s)
- Kris V. Parag
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
| | - Christl A. Donnelly
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
- Department of Statistics, University of Oxford, Oxford, UK
| | - Rahul Jha
- Department of Applied Math and Theoretical Physics, University of Cambridge, Cambridge, UK
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25
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Parag KV, Donnelly CA. Adaptive Estimation for Epidemic Renewal and Phylogenetic Skyline Models. Syst Biol 2020; 69:1163-1179. [PMID: 32333789 PMCID: PMC7584150 DOI: 10.1093/sysbio/syaa035] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 04/14/2020] [Accepted: 04/16/2020] [Indexed: 11/12/2022] Open
Abstract
Estimating temporal changes in a target population from phylogenetic or count data is an important problem in ecology and epidemiology. Reliable estimates can provide key insights into the climatic and biological drivers influencing the diversity or structure of that population and evidence hypotheses concerning its future growth or decline. In infectious disease applications, the individuals infected across an epidemic form the target population. The renewal model estimates the effective reproduction number, R, of the epidemic from counts of observed incident cases. The skyline model infers the effective population size, N, underlying a phylogeny of sequences sampled from that epidemic. Practically, R measures ongoing epidemic growth while N informs on historical caseload. While both models solve distinct problems, the reliability of their estimates depends on p-dimensional piecewise-constant functions. If p is misspecified, the model might underfit significant changes or overfit noise and promote a spurious understanding of the epidemic, which might misguide intervention policies or misinform forecasts. Surprisingly, no transparent yet principled approach for optimizing p exists. Usually, p is heuristically set, or obscurely controlled via complex algorithms. We present a computable and interpretable p-selection method based on the minimum description length (MDL) formalism of information theory. Unlike many standard model selection techniques, MDL accounts for the additional statistical complexity induced by how parameters interact. As a result, our method optimizes p so that R and N estimates properly and meaningfully adapt to available data. It also outperforms comparable Akaike and Bayesian information criteria on several classification problems, given minimal knowledge of the parameter space, and exposes statistical similarities among renewal, skyline, and other models in biology. Rigorous and interpretable model selection is necessary if trustworthy and justifiable conclusions are to be drawn from piecewise models. [Coalescent processes; epidemiology; information theory; model selection; phylodynamics; renewal models; skyline plots].
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Affiliation(s)
- Kris V Parag
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, W2 1PG, UK
| | - Christl A Donnelly
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, W2 1PG, UK
- Department of Statistics, University of Oxford, Oxford, OX1 3LB, UK
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26
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Smith RD, Keogh-Brown MR, Chico RM, Bretscher MT, Drakeley C, Jensen HT. Will More of the Same Achieve Malaria Elimination? Results from an Integrated Macroeconomic Epidemiological Demographic Model. Am J Trop Med Hyg 2020; 103:1871-1882. [PMID: 32959760 PMCID: PMC7646798 DOI: 10.4269/ajtmh.19-0472] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 06/22/2020] [Indexed: 12/20/2022] Open
Abstract
Historic levels of funding have reduced the global burden of malaria in recent years. Questions remain, however, as to whether scaling up interventions, in parallel with economic growth, has made malaria elimination more likely today than previously. The consequences of "trying but failing" to eliminate malaria are also uncertain. Reduced malaria exposure decreases the acquisition of semi-immunity during childhood, a necessary phase of the immunological transition that occurs on the pathway to malaria elimination. During this transitional period, the risk of malaria resurgence increases as proportionately more individuals across all age-groups are less able to manage infections by immune response alone. We developed a robust model that integrates the effects of malaria transmission, demography, and macroeconomics in the context of Plasmodium falciparum malaria within a hyperendemic environment. We analyzed the potential for existing interventions, alongside economic development, to achieve malaria elimination. Simulation results indicate that a 2% increase in future economic growth will increase the US$5.1 billion cumulative economic burden of malaria in Ghana to US$7.2 billion, although increasing regional insecticide-treated net coverage rates by 25% will lower malaria reproduction numbers by just 9%, reduce population-wide morbidity by -0.1%, and reduce prevalence from 54% to 46% by 2034. As scaling up current malaria control tools, combined with economic growth, will be insufficient to interrupt malaria transmission in Ghana, high levels of malaria control should be maintained and investment in research and development should be increased to maintain the gains of the past decade and to minimize the risk of resurgence, as transmission drops.
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Affiliation(s)
- Richard D. Smith
- College of Medicine and Health, University of Exeter, Exeter, United Kingdom
- Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Marcus R. Keogh-Brown
- Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - R. Matthew Chico
- Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Michael T. Bretscher
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College, London, United Kingdom
| | - Chris Drakeley
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Henning Tarp Jensen
- Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Department of Food and Resource Economics, Faculty of Science, University of Copenhagen, Frederiksberg, United Kingdom
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27
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DePina AJ, Stresman G, Barros HSB, Moreira AL, Dia AK, Furtado UD, Faye O, Seck I, Niang EHA. Updates on malaria epidemiology and profile in Cabo Verde from 2010 to 2019: the goal of elimination. Malar J 2020; 19:380. [PMID: 33097051 PMCID: PMC7585190 DOI: 10.1186/s12936-020-03455-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 10/18/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Located in West Africa, Cabo Verde is an archipelago consisting of nine inhabited islands. Malaria has been endemic since the settlement of the islands during the sixteenth century and is poised to achieve malaria elimination in January 2021. The aim of this research is to characterize the trends in malaria cases from 2010 to 2019 in Cabo Verde as the country transitions from endemic transmission to elimination and prevention of reintroduction phases. METHODS All confirmed malaria cases reported to the Ministry of Health between 2010 and 2019 were extracted from the passive malaria surveillance system. Individual-level data available included age, gender, municipality of residence, and the self-reported countries visited if travelled within the past 30 days, therby classified as imported. Trends in reported cases were visualized and multivariable logistic regression used to assess risk factors associated with a malaria case being imported and differences over time. RESULTS A total of 814 incident malaria cases were reported in the country between 2010 and 2019, the majority of which were Plasmodium falciparum. Overall, prior to 2017, when the epidemic occurred, 58.1% (95% CI 53.6-64.6) of infections were classified as imported, whereas during the post-epidemic period, 93.3% (95% CI 86.9-99.7) were imported. The last locally acquired case was reported in January 2018. Imported malaria cases were more likely to be 25-40 years old (AOR: 15.1, 95% CI 5.9-39.2) compared to those under 15 years of age and more likely during the post-epidemic period (AOR: 56.1; 95% CI 13.9-225.5) and most likely to be reported on Sao Vicente Island (AOR = 4256.9, 95% CI = 260-6.9e+4) compared to Boavista. CONCLUSIONS Cabo Verde has made substantial gains in reducing malaria burden in the country over the past decade and are poised to achieve elimination in 2021. However, the high mobility between the islands and continental Africa, where malaria is still highly endemic, means there is a constant risk of malaria reintroduction. Characterization of imported cases provides useful insight for programme and enables better evidence-based decision-making to ensure malaria elimination can be sustained.
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Affiliation(s)
- Adilson José DePina
- Programa de Eliminação do Paludismo, CCS-SIDA, Ministério da Saúde e da Segurança Social, Praia, Cabo Verde.
- Ecole Doctorale des Sciences de la Vie, de la Santé et de l'Environnement (ED-SEV), Université Cheikh Anta Diop (UCAD) de Dakar, Dakar, Sénégal.
| | - Gillian Stresman
- Faculty of Infectious & Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK
| | | | - António Lima Moreira
- Programa Nacional de Luta contra as Doenças de Transmissão vectorial e Problemas de Saúde Associadas ao Meio Ambiente, Ministério da Saúde e da Segurança Social, Praia, Cabo Verde
| | - Abdoulaye Kane Dia
- Ecole Doctorale des Sciences de la Vie, de la Santé et de l'Environnement (ED-SEV), Université Cheikh Anta Diop (UCAD) de Dakar, Dakar, Sénégal
- Laboratoire d'Ecologie Vectorielle et Parasitaire,Faculté des Sciences et Techniques, Université Cheikh Anta Diop (UCAD) de Dakar, Dakar, Sénégal
| | | | - Ousmane Faye
- Laboratoire d'Ecologie Vectorielle et Parasitaire,Faculté des Sciences et Techniques, Université Cheikh Anta Diop (UCAD) de Dakar, Dakar, Sénégal
| | - Ibrahima Seck
- Institut de Santé et Développement, Université Cheikh Anta Diop (UCAD) de Dakar, Dakar, Sénégal
| | - El Hadji Amadou Niang
- Laboratoire d'Ecologie Vectorielle et Parasitaire,Faculté des Sciences et Techniques, Université Cheikh Anta Diop (UCAD) de Dakar, Dakar, Sénégal
- Aix Marseille Univ, IRD, AP-HM, MEPHI, IHU-Méditerranée Infection, Marseille, France
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28
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Brew J, Pradhan M, Broerse J, Bassat Q. Researchers' perceptions of malaria eradication: findings from a mixed-methods analysis of a large online survey. Malar J 2020; 19:359. [PMID: 33032614 PMCID: PMC7545840 DOI: 10.1186/s12936-020-03430-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Accepted: 10/01/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The value of malaria eradication, the permanent reduction to zero of the worldwide incidence of malaria infection caused by human malaria parasites, would be enormous. However, the expected value of an investment in an intended, but uncertain, outcome hinges on the probability of, and time until, its fulfilment. Though the long-term benefits of global malaria eradication promise to be large, the upfront costs and uncertainty regarding feasibility and timeframe make it difficult for policymakers and researchers to forecast the return on investment. METHODS A large online survey of 844 peer-reviewed malaria researchers of different scientific backgrounds administered in order to estimate the probability and time frame of eradication. Adjustments were made for potential selection bias, and thematic analysis of free text comments was carried out. RESULTS The average perceived likelihood of global eradication among malaria researchers approximates the number of years into the future: approximately 10% of researchers believe that eradication will occur in the next 10 years, 30% believe it will occur in the next 30 years, and half believe eradication will require 50 years or more. Researchers who gave free form comments highlighted systemic challenges and the need for innovation as chief among obstacles to achieving global malaria eradication. CONCLUSIONS The findings highlight the difficulty and complexity of malaria eradication, and can be used in prospective cost-benefit analyses to inform stakeholders regarding the likely return on eradication-specific investments.
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Affiliation(s)
- Joe Brew
- Barcelona Institute for Global Health, Hospital Clinic, c/Rosselló, 132, 5è 2a, 08036, Barcelona, Spain. .,Vrije Universiteit Amsterdam, De Boelelaan 1105, 1081 HV, Amsterdam, Netherlands.
| | - Menno Pradhan
- Vrije Universiteit Amsterdam, De Boelelaan 1105, 1081 HV, Amsterdam, Netherlands.,University of Amsterdam, REC E, Roetersstraat 11, Amsterdam, Netherlands
| | - Jacqueline Broerse
- Vrije Universiteit Amsterdam, De Boelelaan 1105, 1081 HV, Amsterdam, Netherlands
| | - Quique Bassat
- Barcelona Institute for Global Health, Hospital Clinic, c/Rosselló, 132, 5è 2a, 08036, Barcelona, Spain.,Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique.,Institució Catalana de Recerca i Estudis Avançats, Pg. Lluís Companys 23, 08010, Barcelona, Spain.,Pediatric Infectious Diseases Unit, Pediatrics Department, Hospital Sant Joan de Déu (University of Barcelona), Barcelona, Spain.,Consorcio de Investigación Biomédica en Red de Epidemiología y Salud Pública, Madrid, Spain
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29
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Sun H, Dickens BL, Cook AR, Clapham HE. Importations of COVID-19 into African countries and risk of onward spread. BMC Infect Dis 2020; 20:598. [PMID: 32791999 PMCID: PMC7424562 DOI: 10.1186/s12879-020-05323-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Accepted: 08/03/2020] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND The emergence of a novel coronavirus (SARS-CoV-2) in Wuhan, China, at the end of 2019 has caused widespread transmission around the world. As new epicentres in Europe and America have arisen, of particular concern is the increased number of imported coronavirus disease 2019 (COVID-19) cases in Africa, where the impact of the pandemic could be more severe. We aim to estimate the number of COVID-19 cases imported from 12 major epicentres in Europe and America to each African country, as well as the probability of reaching 10,000 cases in total by the end of March, April, May, and June following viral introduction. METHODS We used the reported number of cases imported from the 12 major epicentres in Europe and America to Singapore, as well as flight data, to estimate the number of imported cases in each African country. Under the assumption that Singapore has detected all the imported cases, the estimates for Africa were thus conservative. We then propagated the uncertainty in the imported case count estimates to simulate the onward spread of the virus, until 10,000 cases are reached or the end of June, whichever is earlier. Specifically, 1,000 simulations were run separately under four different combinations of parameter values to test the sensitivity of our results. RESULTS We estimated Morocco, Algeria, South Africa, Egypt, Tunisia, and Nigeria as having the largest number of COVID-19 cases imported from the 12 major epicentres. Based on our 1,000 simulation runs, Morocco and Algeria's estimated probability of reaching 10,000 cases by end of March was close to 100% under all scenarios. In particular, we identified countries with less than 1,000 cases in total reported by end of June whilst the estimated probability of reaching 10,000 cases by then was higher than 50% even under the most optimistic scenario. CONCLUSIONS Our study highlights particular countries that are likely to reach (or have reached) 10,000 cases far earlier than the reported data suggest, calling for the prioritization of resources to mitigate the further spread of the epidemic.
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Affiliation(s)
- Haoyang Sun
- Saw Swee Hock School of Public Health, National University of Singapore, 12 Science Drive 2, Singapore, 117549, Republic of Singapore.
| | - Borame L Dickens
- Saw Swee Hock School of Public Health, National University of Singapore, 12 Science Drive 2, Singapore, 117549, Republic of Singapore
| | - Alex R Cook
- Saw Swee Hock School of Public Health, National University of Singapore, 12 Science Drive 2, Singapore, 117549, Republic of Singapore
| | - Hannah E Clapham
- Saw Swee Hock School of Public Health, National University of Singapore, 12 Science Drive 2, Singapore, 117549, Republic of Singapore.
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30
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Cirera L, Galatas B, Alonso S, Paaijmans K, Mamuquele M, Martí-Soler H, Guinovart C, Munguambe H, Luis F, Nhantumbo H, Montañà J, Bassat Q, Candrinho B, Rabinovich R, Macete E, Aide P, Alonso P, Saúte F, Sicuri E. Moving towards malaria elimination in southern Mozambique: Cost and cost-effectiveness of mass drug administration combined with intensified malaria control. PLoS One 2020; 15:e0235631. [PMID: 32628741 PMCID: PMC7337313 DOI: 10.1371/journal.pone.0235631] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 06/08/2020] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND As new combinations of interventions aiming at interrupting malaria transmission are under evaluation, understanding the associated economic costs and benefits is critical for decision-making. This study assessed the economic cost and cost-effectiveness of the Magude project, a malaria elimination initiative implemented in a district in southern Mozambique (i.e. Magude) between August 2015-June 2018. This project piloted a combination of two mass drug administration (MDA) rounds per year for two consecutive years, annual rounds of universal indoor residual spraying (IRS) and a strengthened surveillance and response system on the back of universal long-lasting insecticide treated net (LLIN) coverage and routine case management implemented by the National Malaria Control Program (NMCP). Although local transmission was not interrupted, the project achieved large reductions in the burden of malaria in the target district. METHODS We collected weekly economic data, estimated costs from the project implementer perspective and assessed the incremental cost-effectiveness ratio (ICER) associated with the Magude project as compared to routine malaria control activities, the counterfactual. We estimated disability-adjusted life years (DALYs) for malaria cases and deaths and assessed the variation of the ICER over time to capture the marginal costs and effectiveness associated with subsequent phases of project implementation. We used deterministic and probabilistic sensitivity analyses to account for uncertainty and built an alternative scenario by assuming the implementation of the interventions from a governmental perspective. Economic costs are provided in constant US$2015. RESULTS After three years, the Magude project averted a total of 3,171 DALYs at an incremental cost of $2.89 million and an average yearly cost of $20.7 per targeted person. At an average cost of $19.4 per person treated per MDA round, the social mobilization and distribution of door-to-door MDA contributed to 53% of overall resources employed, with personnel and logistics being the main cost drivers. The ICER improved over time as a result of decreasing costs and improved effectiveness. The overall ICER was $987 (CI95% 968-1,006) per DALY averted, which is below the standard cost-effectiveness (CE) threshold of $1,404/DALY averted, three times the gross domestic product (GDP) per capita of Mozambique, but above the threshold of interventions considered highly cost-effective (one time the GDP per capita or $468/DALY averted) and above the recently suggested thresholds based on the health opportunity cost ($537 purchasing power parity/ DALY averted). A significantly lower ICER was obtained in the implementation scenario from a governmental perspective ($441/DALY averted). CONCLUSION Despite the initial high costs and volume of resources associated with its implementation, MDA in combination with other existing malaria control interventions, can be a cost-effective strategy to drastically reduce transmission in areas of low to moderate transmission in sub-Saharan Africa. However, further studies are needed to understand the capacity of the health system and financial affordability to scale up such strategies at regional or national level.
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Affiliation(s)
- Laia Cirera
- ISGlobal, Hospital Clínic -Universitat de Barcelona, Barcelona, Spain
| | - Beatriz Galatas
- ISGlobal, Hospital Clínic -Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde da Manhiça (CISM), Manhiça, Mozambique
| | - Sergi Alonso
- Centre for Primary Care and Public Health, Barts and The London School of Medicine & Dentistry, Queen Mary University of London, London, United Kingdom
| | - Krijn Paaijmans
- ISGlobal, Hospital Clínic -Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde da Manhiça (CISM), Manhiça, Mozambique
- Center for Evolution and Medicine & The Biodesign Center for Immunotherapy, Vaccines and Virotherapy, School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | - Miler Mamuquele
- Centro de Investigação em Saúde da Manhiça (CISM), Manhiça, Mozambique
| | | | | | | | - Fabião Luis
- Centro de Investigação em Saúde da Manhiça (CISM), Manhiça, Mozambique
| | - Hoticha Nhantumbo
- Centro de Investigação em Saúde da Manhiça (CISM), Manhiça, Mozambique
| | - Júlia Montañà
- ISGlobal, Hospital Clínic -Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde da Manhiça (CISM), Manhiça, Mozambique
| | - Quique Bassat
- ISGlobal, Hospital Clínic -Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde da Manhiça (CISM), Manhiça, Mozambique
- Pediatric Infectious Diseases Unit, Pediatrics Department, Hospital Sant Joan de Déu (University of Barcelona), Barcelona, Spain
- ICREA, Barcelona, Spain
| | - Baltazar Candrinho
- National Malaria Control Program, Ministry of Health, Maputo, Mozambique
| | - Regina Rabinovich
- ISGlobal, Hospital Clínic -Universitat de Barcelona, Barcelona, Spain
- Harvard T.H. Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Eusebio Macete
- Centro de Investigação em Saúde da Manhiça (CISM), Manhiça, Mozambique
- National Institute of Health, Ministry of Health, Maputo, Mozambique
| | - Pedro Aide
- Centro de Investigação em Saúde da Manhiça (CISM), Manhiça, Mozambique
- National Institute of Health, Ministry of Health, Maputo, Mozambique
| | - Pedro Alonso
- ISGlobal, Hospital Clínic -Universitat de Barcelona, Barcelona, Spain
- Centro de Investigação em Saúde da Manhiça (CISM), Manhiça, Mozambique
| | - Francisco Saúte
- Centro de Investigação em Saúde da Manhiça (CISM), Manhiça, Mozambique
| | - Elisa Sicuri
- ISGlobal, Hospital Clínic -Universitat de Barcelona, Barcelona, Spain
- Department of Infectious Disease Epidemiology, Health Economics Group, School of Public Health, Imperial College London, London, United Kingdom
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31
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Roh ME, Tessema SK, Murphy M, Nhlabathi N, Mkhonta N, Vilakati S, Ntshalintshali N, Saini M, Maphalala G, Chen A, Wilheim J, Prach L, Gosling R, Kunene S, S Hsiang M, Greenhouse B. High Genetic Diversity of Plasmodium falciparum in the Low-Transmission Setting of the Kingdom of Eswatini. J Infect Dis 2020; 220:1346-1354. [PMID: 31190073 PMCID: PMC6743842 DOI: 10.1093/infdis/jiz305] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 06/12/2019] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND To better understand transmission dynamics, we characterized Plasmodium falciparum genetic diversity in Eswatini, where transmission is low and sustained by importation. METHODS Twenty-six P. falciparum microsatellites were genotyped in 66% of confirmed cases (2014-2016; N = 582). Population and within-host diversity were used to characterize differences between imported and locally acquired infections. Logistic regression was used to assess the added value of diversity metrics to classify imported and local infections beyond epidemiology data alone. RESULTS Parasite population in Eswatini was highly diverse (expected heterozygosity [HE] = 0.75) and complex: 67% polyclonal infections, mean multiplicity of infection (MOI) 2.2, and mean within-host infection fixation index (FWS) 0.84. Imported cases had comparable diversity to local cases but exhibited higher MOI (2.4 vs 2.0; P = .004) and lower mean FWS (0.82 vs 0.85; P = .03). Addition of MOI and FWS to multivariate analyses did not increase discrimination between imported and local infections. CONCLUSIONS In contrast to the common perception that P. falciparum diversity declines with decreasing transmission intensity, Eswatini isolates exhibited high parasite diversity consistent with high rates of malaria importation and limited local transmission. Estimates of malaria transmission intensity from genetic data need to consider the effect of importation, especially as countries near elimination.
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Affiliation(s)
- Michelle E Roh
- Malaria Elimination Initiative, Institute of Global Health Sciences, University of California, San Francisco.,Department of Epidemiology and Biostatistics, University of California, San Francisco
| | - Sofonias K Tessema
- Division of HIV, Infectious Diseases, and Global Medicine, Department of Medicine, University of California, San Francisco
| | - Maxwell Murphy
- Division of HIV, Infectious Diseases, and Global Medicine, Department of Medicine, University of California, San Francisco
| | | | | | | | | | - Manik Saini
- Clinton Health Access Initiative, Mbabane, Eswatini
| | | | - Anna Chen
- Division of HIV, Infectious Diseases, and Global Medicine, Department of Medicine, University of California, San Francisco
| | - Jordan Wilheim
- Division of HIV, Infectious Diseases, and Global Medicine, Department of Medicine, University of California, San Francisco
| | - Lisa Prach
- Malaria Elimination Initiative, Institute of Global Health Sciences, University of California, San Francisco
| | - Roly Gosling
- Malaria Elimination Initiative, Institute of Global Health Sciences, University of California, San Francisco.,Department of Epidemiology and Biostatistics, University of California, San Francisco
| | | | - Michelle S Hsiang
- Malaria Elimination Initiative, Institute of Global Health Sciences, University of California, San Francisco.,Department of Pediatrics, University of California, San Francisco.,Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas
| | - Bryan Greenhouse
- Division of HIV, Infectious Diseases, and Global Medicine, Department of Medicine, University of California, San Francisco.,Chan Zuckerberg Biohub, San Francisco, California
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32
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McLure A, Glass K. Some simple rules for estimating reproduction numbers in the presence of reservoir exposure or imported cases. Theor Popul Biol 2020; 134:182-194. [PMID: 32304644 PMCID: PMC7159883 DOI: 10.1016/j.tpb.2020.04.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 03/29/2020] [Accepted: 04/10/2020] [Indexed: 02/04/2023]
Abstract
For many diseases, the basic reproduction number (R0) is a threshold parameter for disease extinction or survival in isolated populations. However no human population is fully isolated from other human or animal populations. We use compartmental models to derive simple rules for the basic reproduction number in populations where an endemic disease is sustained by a combination of local transmission within the population and exposure from some other source: either a reservoir exposure or imported cases. We introduce the idea of a reservoir-driven or importation-driven disease: diseases that would become extinct in the population of interest without reservoir exposure or imported cases (since R0<1), but nevertheless may be sufficiently transmissible that many or most infections are acquired from humans in that population. We show that in the simplest case, R0<1 if and only if the proportion of infections acquired from the external source exceeds the disease prevalence and explore how population heterogeneity and the interactions of multiple strains affect this rule. We apply these rules in two case studies of Clostridium difficile infection and colonisation: C. difficile in the hospital setting accounting for imported cases, and C. difficile in the general human population accounting for exposure to animal reservoirs. We demonstrate that even the hospital-adapted, highly-transmissible NAP1/RT027 strain of C. difficile had a reproduction number <1 in a landmark study of hospitalised patients and therefore was sustained by colonised and infected admissions to the study hospital. We argue that C. difficile should be considered reservoir-driven if as little as 13.0% of transmission can be attributed to animal reservoirs.
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Affiliation(s)
- Angus McLure
- Research School of Population Health, Australian National University, 62 Mills Rd, Acton, 0200, ACT, Australia.
| | - Kathryn Glass
- Research School of Population Health, Australian National University, 62 Mills Rd, Acton, 0200, ACT, Australia
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33
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Routledge I, Lai S, Battle KE, Ghani AC, Gomez-Rodriguez M, Gustafson KB, Mishra S, Unwin J, Proctor JL, Tatem AJ, Li Z, Bhatt S. Tracking progress towards malaria elimination in China: Individual-level estimates of transmission and its spatiotemporal variation using a diffusion network approach. PLoS Comput Biol 2020; 16:e1007707. [PMID: 32203520 PMCID: PMC7117777 DOI: 10.1371/journal.pcbi.1007707] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 04/02/2020] [Accepted: 02/03/2020] [Indexed: 01/02/2023] Open
Abstract
In order to monitor progress towards malaria elimination, it is crucial to be able to measure changes in spatio-temporal transmission. However, common metrics of malaria transmission such as parasite prevalence are under powered in elimination contexts. China has achieved major reductions in malaria incidence and is on track to eliminate, having reporting zero locally-acquired malaria cases in 2017 and 2018. Understanding the spatio-temporal pattern underlying this decline, especially the relationship between locally-acquired and imported cases, can inform efforts to maintain elimination and prevent re-emergence. This is particularly pertinent in Yunnan province, where the potential for local transmission is highest. Using a geo-located individual-level dataset of cases recorded in Yunnan province between 2011 and 2016, we introduce a novel Bayesian framework to model a latent diffusion process and estimate the joint likelihood of transmission between cases and the number of cases with unobserved sources of infection. This is used to estimate the case reproduction number, Rc. We use these estimates within spatio-temporal geostatistical models to map how transmission varied over time and space, estimate the timeline to elimination and the risk of resurgence. We estimate the mean Rc between 2011 and 2016 to be 0.171 (95% CI = 0.165, 0.178) for P. vivax cases and 0.089 (95% CI = 0.076, 0.103) for P. falciparum cases. From 2014 onwards, no cases were estimated to have a Rc value above one. An unobserved source of infection was estimated to be moderately likely (p>0.5) for 19/ 611 cases and high (p>0.8) for 2 cases, suggesting very high levels of case ascertainment. Our estimates suggest that, maintaining current intervention efforts, Yunnan is unlikely to experience sustained local transmission up to 2020. However, even with a mean of 0.005 projected up to 2020, locally-acquired cases are possible due to high levels of importation.
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Affiliation(s)
| | - Shengjie Lai
- University of Southampton, Southampton, United Kingdom
| | | | | | | | - Kyle B. Gustafson
- Institute for Disease Modelling, Bellevue, Washington, United States of America
| | | | | | - Joshua L. Proctor
- Institute for Disease Modelling, Bellevue, Washington, United States of America
| | | | - Zhongjie Li
- Chinese Centers for Disease Control and Prevention, Beijing, China
| | - Samir Bhatt
- Imperial College London, London, United Kingom
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34
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Bridges DJ, Chishimba S, Mwenda M, Winters AM, Slawsky E, Mambwe B, Mulube C, Searle KM, Hakalima A, Mwenechanya R, Larsen DA. The use of spatial and genetic tools to assess Plasmodium falciparum transmission in Lusaka, Zambia between 2011 and 2015. Malar J 2020; 19:20. [PMID: 31941493 PMCID: PMC6964105 DOI: 10.1186/s12936-020-3101-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Accepted: 01/07/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Zambia has set itself the ambitious target of eliminating malaria by 2021. To continue tracking transmission to zero, new interventions, tools and approaches are required. METHODS Urban reactive case detection (RCD) was performed in Lusaka city from 2011 to 2015 to better understand the location and drivers of malaria transmission. Briefly, index cases were followed to their home and all consenting individuals living in the index house and nine proximal houses were tested with a malaria rapid diagnostic test and treated if positive. A brief survey was performed and for certain responses, a dried blood spot sample collected for genetic analysis. Aggregate health facility data, individual RCD response data and genetic results were analysed spatially and against environmental correlates. RESULTS Total number of malaria cases remained relatively constant, while the average age of incident cases and the proportion of incident cases reporting recent travel both increased. The estimated R0 in Lusaka was < 1 throughout the study period. RCD responses performed within 250 m of uninhabited/vacant land were associated with a higher probability of identifying additional infections. CONCLUSIONS Evidence suggests that the majority of malaria infections are imported from outside Lusaka. However there remains some level of local transmission occurring on the periphery of urban settlements, namely in the wet season. Unfortunately, due to the higher-than-expected complexity of infections and the small number of samples tested, genetic analysis was unable to identify any meaningful trends in the data.
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Affiliation(s)
- Daniel J Bridges
- PATH MACEPA, National Malaria Elimination Centre, Gt East Rd, Lusaka, Zambia. .,Akros, 45A Roan Road, Lusaka, Zambia.
| | - Sandra Chishimba
- PATH MACEPA, National Malaria Elimination Centre, Gt East Rd, Lusaka, Zambia.,Akros, 45A Roan Road, Lusaka, Zambia
| | - Mulenga Mwenda
- PATH MACEPA, National Malaria Elimination Centre, Gt East Rd, Lusaka, Zambia.,Akros, 45A Roan Road, Lusaka, Zambia
| | - Anna M Winters
- Akros, 45A Roan Road, Lusaka, Zambia.,School of Public and Community Health Sciences, University of Montana, Missoula, MT, USA
| | - Erik Slawsky
- Department of Public Health, Syracuse University, Syracuse, NY, USA
| | - Brenda Mambwe
- PATH MACEPA, National Malaria Elimination Centre, Gt East Rd, Lusaka, Zambia
| | - Conceptor Mulube
- PATH MACEPA, National Malaria Elimination Centre, Gt East Rd, Lusaka, Zambia
| | - Kelly M Searle
- School of Public Health, University of Minnesota, Minneapolis, MN, USA
| | - Aves Hakalima
- Lusaka District Health Management Team, Ministry of Health, Lusaka, Zambia
| | - Roy Mwenechanya
- Akros, 45A Roan Road, Lusaka, Zambia.,Department of Biomedical Sciences, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia
| | - David A Larsen
- Akros, 45A Roan Road, Lusaka, Zambia.,Department of Public Health, Syracuse University, Syracuse, NY, USA
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35
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Guerra CA, Citron DT, García GA, Smith DL. Characterising malaria connectivity using malaria indicator survey data. Malar J 2019; 18:440. [PMID: 31870353 PMCID: PMC6929427 DOI: 10.1186/s12936-019-3078-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Accepted: 12/14/2019] [Indexed: 12/13/2022] Open
Abstract
Malaria connectivity describes the flow of parasites among transmission sources and sinks within a given landscape. Because of the spatial and temporal scales at which parasites are transported by their hosts, malaria sub-populations are largely defined by mosquito movement and malaria connectivity among them is largely driven by human movement. Characterising malaria connectivity thus requires characterising human travel between areas with differing levels of exposure to malaria. Whilst understanding malaria connectivity is fundamental for optimising interventions, particularly in areas seeking or sustaining elimination, there is a dearth of human movement data required to achieve this goal. Malaria indicator surveys (MIS) are a generally under utilised but potentially rich source of travel data that provide a unique opportunity to study simple associations between malaria infection and human travel in large population samples. This paper shares the experience working with MIS data from Bioko Island that revealed programmatically useful information regarding malaria importation through human travel. Simple additions to MIS questionnaires greatly augmented the level of detail of the travel data, which can be used to characterise human travel patterns and malaria connectivity to assist targeting interventions. It is argued that MIS potentially represent very important and timely sources of travel data that need to be further exploited.
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Affiliation(s)
- Carlos A Guerra
- Medical Care Development International, 8401 Colesville Road, Suite 425, Silver Spring, MD, 20910, USA.
| | - Daniel T Citron
- Institute for Health Metrics and Evaluation, University of Washington, 2301 Fifth Avenue, Seattle, 98121, USA
| | - Guillermo A García
- Medical Care Development International, 8401 Colesville Road, Suite 425, Silver Spring, MD, 20910, USA
| | - David L Smith
- Institute for Health Metrics and Evaluation, University of Washington, 2301 Fifth Avenue, Seattle, 98121, USA
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36
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Narula AK, Azad CS, Nainwal LM. New dimensions in the field of antimalarial research against malaria resurgence. Eur J Med Chem 2019; 181:111353. [DOI: 10.1016/j.ejmech.2019.05.043] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 04/16/2019] [Accepted: 05/15/2019] [Indexed: 12/20/2022]
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37
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Malinga J, Maia M, Moore S, Ross A. Can trials of spatial repellents be used to estimate mosquito movement? Parasit Vectors 2019; 12:421. [PMID: 31477155 PMCID: PMC6720076 DOI: 10.1186/s13071-019-3662-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2019] [Accepted: 08/09/2019] [Indexed: 11/16/2022] Open
Abstract
Background Knowledge of mosquito movement would aid the design of effective intervention strategies against malaria. However, data on mosquito movement through mark-recapture or genetics studies are challenging to collect, and so are not available for many sites. An additional source of information may come from secondary analyses of data from trials of repellents where household mosquito densities are collected. Using the study design of published trials, we developed a statistical model which can be used to estimate the movement between houses for mosquitoes displaced by a spatial repellent. The method uses information on the different distributions of mosquitoes between houses when no households are using spatial repellents compared to when there is incomplete coverage. The parameters to be estimated are the proportion of mosquitoes repelled, the proportion of those repelled that go to another house and the mean distance of movement between houses. Estimation is by maximum likelihood. Results We evaluated the method using simulation and found that data on the seasonal pattern of mosquito densities were required, which could be additionally collected during a trial. The method was able to provide accurate estimates from simulated data, except when the setting has few mosquitoes overall, few repelled, or the coverage with spatial repellent is low. The trial that motivated our analysis was found to have too few mosquitoes caught and repelled for our method to provide accurate results. Conclusions We propose that the method could be used as a secondary analysis of trial data to gain estimates of mosquito movement in the presence of repellents for trials with sufficient numbers of mosquitoes caught and repelled and with coverage levels which allow sufficient numbers of houses with and without repellent. Estimates from this method may supplement those from mark-release-recapture studies, and be used in designing effective malaria intervention strategies, parameterizing mathematical models and in designing trials of vector control interventions.
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Affiliation(s)
- Josephine Malinga
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Marta Maia
- KEMRI Wellcome Trust Research Programme, Kilifi, Kenya.,Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
| | - Sarah Moore
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland.,Ifakara Health Institute, Ifakara, Tanzania
| | - Amanda Ross
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
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38
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Fox SJ, Bellan SE, Perkins TA, Johansson MA, Meyers LA. Downgrading disease transmission risk estimates using terminal importations. PLoS Negl Trop Dis 2019; 13:e0007395. [PMID: 31199809 PMCID: PMC6594658 DOI: 10.1371/journal.pntd.0007395] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 06/26/2019] [Accepted: 04/16/2019] [Indexed: 12/19/2022] Open
Abstract
As emerging and re-emerging infectious arboviruses like dengue, chikungunya, and Zika threaten new populations worldwide, officials scramble to assess local severity and transmissibility, with little to no epidemiological history to draw upon. Indirect estimates of risk from vector habitat suitability maps are prone to great uncertainty, while direct estimates from epidemiological data are only possible after cases accumulate and, given environmental constraints on arbovirus transmission, cannot be widely generalized beyond the focal region. Combining these complementary methods, we use disease importation and transmission data to improve the accuracy and precision of a priori ecological risk estimates. We demonstrate this approach by estimating the spatiotemporal risks of Zika virus transmission throughout Texas, a high-risk region in the southern United States. Our estimates are, on average, 80% lower than published ecological estimates-with only six of 254 Texas counties deemed capable of sustaining a Zika epidemic-and they are consistent with the number of autochthonous cases detected in 2017. Importantly our method provides a framework for model comparison, as our mechanistic understanding of arbovirus transmission continues to improve. Real-time updating of prior risk estimates as importations and outbreaks arise can thereby provide critical, early insight into local transmission risks as emerging arboviruses expand their global reach.
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Affiliation(s)
- Spencer J. Fox
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas, United States of America
| | - Steven E. Bellan
- Department of Epidemiology and Biostatistics, University of Georgia, Athens, Georgia, United States of America
- Center for Ecology of Infectious Diseases, University of Georgia, Athens, Gerogia, United States of America
| | - T. Alex Perkins
- Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Michael A. Johansson
- Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, San Juan, Puerto Rico
- Center for Communicable Disease Dynamics, Harvard TH Chan School of Public Health, Boston, Massachusetts, United States of America
| | - Lauren Ancel Meyers
- Department of Integrative Biology, University of Texas at Austin, Austin, Texas, United States of America
- Santa Fe Institute, Santa Fe, New Mexico, United States of America
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39
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The economics of malaria control in an age of declining aid. Nat Commun 2019; 10:2269. [PMID: 31138799 PMCID: PMC6538702 DOI: 10.1038/s41467-019-09991-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 04/11/2019] [Indexed: 11/09/2022] Open
Abstract
This article examines financing in the fight against malaria. After briefly describing malaria control plans in Africa since 2000, it offers a stylized model of the economics of malaria and shows how health aid can help escape the malaria trap.
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40
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Smith JL, Ghimire P, Rijal KR, Maglior A, Hollis S, Andrade-Pacheco R, Das Thakur G, Adhikari N, Thapa Shrestha U, Banjara MR, Lal BK, Jacobson JO, Bennett A. Designing malaria surveillance strategies for mobile and migrant populations in Nepal: a mixed-methods study. Malar J 2019; 18:158. [PMID: 31053075 PMCID: PMC6500027 DOI: 10.1186/s12936-019-2791-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 04/23/2019] [Indexed: 11/10/2022] Open
Abstract
Background As malaria cases have declined throughout Nepal, imported cases comprise an increasing share of the remaining malaria caseload, yet how to effectively target mobile and migrant populations (MMPs) at greatest risk is not well understood. This formative research aimed to confirm the link between imported and indigenous cases, characterize high-risk MMPs, and identify opportunities to adapt surveillance and intervention strategies to them. Methods The study used a mixed-methods approach in three districts in far and mid-western Nepal, including (i) a retrospective analysis of passive surveillance data, (ii) a quantitative health facility-based survey of imported cases and their MMP social contacts recruited by peer-referral, and (iii) focus group (FG) discussions and key informant interviews (KIIs) with a subset of survey participants. Retrospective case data were summarised and the association between monthly indigenous case counts and importation rates in the previous month was investigated using Bayesian spatio-temporal regression models. Quantitative data from structured interviews were summarised to develop profiles of imported cases and MMP contacts, including travel characteristics and malaria knowledge, attitudes and practice. Descriptive statistics of the size of cases’ MMP social networks are presented as a measure of potential programme reach. To explore opportunities and barriers for targeted malaria surveillance, data from FGs and KIIs were formally analysed using a thematic content analysis approach. Results More than half (54.1%) of malaria cases between 2013 and 2016 were classified as imported and there was a positive association between monthly indigenous cases (incidence rate ratio (IRR) 1.02 95% CI 1.01–1.03) and the previous month’s case importation rate. High-risk MMPs were identified as predominantly adult male labourers, who travel to malaria endemic areas of India, often lack a basic understanding of malaria transmission and prevention, rarely use ITNs while travelling and tend not to seek treatment when ill or prefer informal private providers. Important obstacles were identified to accessing Nepali MMPs at border crossings and at workplaces within India. However, strong social connectivity during travel and while in India, as well as return to Nepal for large seasonal festivals, provide opportunities for peer-referral-based and venue-based surveillance and intervention approaches, respectively. Conclusions Population mobility and imported malaria cases from India may help to drive local transmission in border areas of far and mid-western Nepal. Enhanced surveillance targeting high-risk MMP subgroups would improve early malaria diagnosis and treatment, as well as provide a platform for education and intervention campaigns. A combination of community-based approaches is likely necessary to achieve malaria elimination in Nepal. Electronic supplementary material The online version of this article (10.1186/s12936-019-2791-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Jennifer L Smith
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco, USA
| | - Prakash Ghimire
- Central Department of Microbiology, Tribhuvan University, Kirtipur, Kathmandu, Nepal.
| | - Komal Raj Rijal
- Central Department of Microbiology, Tribhuvan University, Kirtipur, Kathmandu, Nepal
| | - Alysse Maglior
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco, USA
| | - Sara Hollis
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco, USA
| | - Ricardo Andrade-Pacheco
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco, USA
| | - Garib Das Thakur
- Epidemiology and Diseases Control Division, Ministry of Health and Population, Teku, Kathmandu, Nepal
| | - Nabaraj Adhikari
- Central Department of Microbiology, Tribhuvan University, Kirtipur, Kathmandu, Nepal
| | | | - Megha Raj Banjara
- Central Department of Microbiology, Tribhuvan University, Kirtipur, Kathmandu, Nepal
| | - Bibek Kumar Lal
- Epidemiology and Diseases Control Division, Ministry of Health and Population, Teku, Kathmandu, Nepal
| | - Jerry O Jacobson
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco, USA
| | - Adam Bennett
- Malaria Elimination Initiative, Global Health Group, University of California, San Francisco, USA
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41
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Chang HH, Wesolowski A, Sinha I, Jacob CG, Mahmud A, Uddin D, Zaman SI, Hossain MA, Faiz MA, Ghose A, Sayeed AA, Rahman MR, Islam A, Karim MJ, Rezwan MK, Shamsuzzaman AKM, Jhora ST, Aktaruzzaman MM, Drury E, Gonçalves S, Kekre M, Dhorda M, Vongpromek R, Miotto O, Engø-Monsen K, Kwiatkowski D, Maude RJ, Buckee C. Mapping imported malaria in Bangladesh using parasite genetic and human mobility data. eLife 2019; 8:43481. [PMID: 30938289 PMCID: PMC6478433 DOI: 10.7554/elife.43481] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Accepted: 03/14/2019] [Indexed: 01/25/2023] Open
Abstract
For countries aiming for malaria elimination, travel of infected individuals between endemic areas undermines local interventions. Quantifying parasite importation has therefore become a priority for national control programs. We analyzed epidemiological surveillance data, travel surveys, parasite genetic data, and anonymized mobile phone data to measure the spatial spread of malaria parasites in southeast Bangladesh. We developed a genetic mixing index to estimate the likelihood of samples being local or imported from parasite genetic data and inferred the direction and intensity of parasite flow between locations using an epidemiological model integrating the travel survey and mobile phone calling data. Our approach indicates that, contrary to dogma, frequent mixing occurs in low transmission regions in the southwest, and elimination will require interventions in addition to reducing imported infections from forested regions. Unlike risk maps generated from clinical case counts alone, therefore, our approach distinguishes areas of frequent importation as well as high transmission.
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Affiliation(s)
- Hsiao-Han Chang
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, United States.,The Center for Communicable Disease Dynamics, Harvard T.H. Chan School of Public Health, Boston, United States
| | - Amy Wesolowski
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, United States
| | - Ipsita Sinha
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | | | - Ayesha Mahmud
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, United States.,The Center for Communicable Disease Dynamics, Harvard T.H. Chan School of Public Health, Boston, United States
| | - Didar Uddin
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Sazid Ibna Zaman
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Md Amir Hossain
- Department of Medicine, Chittagong Medical College, Chittagong, Bangladesh
| | - M Abul Faiz
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Dev Care Foundation, Dhaka, Bangladesh
| | | | | | | | | | | | - M Kamar Rezwan
- Vector-Borne Disease Control, World Health Organization, Dhaka, Bangladesh
| | | | - Sanya Tahmina Jhora
- Communicable Disease Control, Directorate General of Health Services, Dhaka, Bangladesh
| | | | - Eleanor Drury
- Wellcome Sanger Institute, Cambridge, United Kingdom
| | | | - Mihir Kekre
- Wellcome Sanger Institute, Cambridge, United Kingdom
| | - Mehul Dhorda
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom.,Worldwide Antimalarial Resistance Network, Asia Regional Centre, Bangkok, Thailand
| | - Ranitha Vongpromek
- Worldwide Antimalarial Resistance Network, Asia Regional Centre, Bangkok, Thailand
| | - Olivo Miotto
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Wellcome Sanger Institute, Cambridge, United Kingdom.,Big Data Institute, Oxford University, Oxford, United Kingdom
| | | | - Dominic Kwiatkowski
- Wellcome Sanger Institute, Cambridge, United Kingdom.,Big Data Institute, Oxford University, Oxford, United Kingdom
| | - Richard J Maude
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, United States.,The Center for Communicable Disease Dynamics, Harvard T.H. Chan School of Public Health, Boston, United States.,Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Caroline Buckee
- Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, United States.,The Center for Communicable Disease Dynamics, Harvard T.H. Chan School of Public Health, Boston, United States
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42
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Balawanth R, Ba I, Qwabe B, Gast L, Maharaj R, Raman J, Graffy R, Shandukani M, Moonasar D. Assessing Kwa-Zulu-Natal's progress towards malaria elimination and its readiness for sub-national verification. Malar J 2019; 18:108. [PMID: 30935418 PMCID: PMC6444529 DOI: 10.1186/s12936-019-2739-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Accepted: 03/20/2019] [Indexed: 11/24/2022] Open
Abstract
Background The South African province of KwaZulu-Natal is rapidly approaching elimination status for malaria with a steady decline in local cases. With the possibility of achieving elimination in reach, the KZN malaria control programme conducted a critical evaluation of its practices and protocols to identify potential challenges and priorities to achieving elimination. Three fundamental questions were addressed: (1) How close is KZN to malaria elimination; (2) Are all systems required to pursue subnational verification of elimination in place; and (3) What priority interventions must be implemented to reduce local cases to zero? Methods Based on the 2017 World Health Organization Framework for Elimination, twenty-eight requirements were identified, from which forty-nine indicators to grade elimination progress were further stratified. Malaria data were extracted from the surveillance system and other programme data sources to calculate each indicator and semi-quantitatively rate performance into one of four categories to assess the provinces elimination preparedness. Results Across the key components a number of gaps were elucidated based on specific indicators. Out of the 49 indicators across these key components, 10 indicators (20%) were rated as fully implemented/well implemented, 11 indicators (22%) were rated as partially done/somewhat implemented/activity needs to be strengthened, and 12 indicators (24%) were rated as not done at all/not implemented/poor performance. Sixteen indicators (33%) could not be calculated due to lack of data or missing data. Conclusions The critical self-evaluation of programme performance has allowed the KZN malaria programme to plan to address key issues moving forward. Based on the findings from the checklist review process, planning exercises were conducted to improve lower-rating indicators, and a monitoring and evaluation framework was created to assess progress on a monthly basis. This is scheduled to be reviewed annually to ensure continued progress toward meeting the elimination goal. In addition, multiple dissemination meetings were held with both provincial senior management and operational staff to ensure ownership of the checklist and its action plan at all levels. Electronic supplementary material The online version of this article (10.1186/s12936-019-2739-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ryleen Balawanth
- Clinton Health Access Initiative, Pretoria, Gauteng, South Africa.
| | - Inessa Ba
- Clinton Health Access Initiative, Pretoria, Gauteng, South Africa
| | - Bheki Qwabe
- KwaZulu-Natal Department of Health, Jozini, KwaZulu-Natal, South Africa
| | - Laura Gast
- Clinton Health Access Initiative, Pretoria, Gauteng, South Africa
| | - Rajendra Maharaj
- South African Medical Research Council, Durban, KwaZulu-Natal, South Africa
| | - Jaishree Raman
- National Institute of Communicable Disease, Sandringham, Gauteng, South Africa
| | - Rebecca Graffy
- Clinton Health Access Initiative, Pretoria, Gauteng, South Africa
| | - Mbavhalelo Shandukani
- National Institute of Communicable Disease, Sandringham, Gauteng, South Africa.,South Africa National Department of Health, Pretoria, Gauteng, South Africa
| | - Devanand Moonasar
- National Institute of Communicable Disease, Sandringham, Gauteng, South Africa.,South Africa National Department of Health, Pretoria, Gauteng, South Africa
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43
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Dhiman S. Are malaria elimination efforts on right track? An analysis of gains achieved and challenges ahead. Infect Dis Poverty 2019; 8:14. [PMID: 30760324 PMCID: PMC6375178 DOI: 10.1186/s40249-019-0524-x] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Accepted: 01/31/2019] [Indexed: 01/30/2023] Open
Abstract
Background Malaria causes significant morbidity and mortality each year. In the past few years, the global malaria cases have been declining and many endemic countries are heading towards malaria elimination. Nevertheless, reducing the number of cases seems to be easy than sustained elimination. Therefore to achieve the objective of complete elimination and maintaining the elimination status, it is necessary to assess the gains made during the recent years. Main text With inclining global support and World Health Organisation (WHO) efforts, the control programmes have been implemented effectively in many endemic countries. Given the aroused interest and investments into malaria elimination programmes at global level, the ambitious goal of elimination appears feasible. Sustainable interventions have played a pivotal role in malaria contraction, however drug and insecticide resistance, social, demographic, cultural and behavioural beliefs and practices, and unreformed health infrastructure could drift back the progress attained so far. Ignoring such impeding factors coupled with certain region specific factors may jeopardise our ability to abide righteous track to achieve global elimination of malaria parasite. Although support beyond the territories is important, but well managed integrated vector management approach at regional and country level using scrupulously selected area specific interventions targeting both vector and parasite along with the community involvement is necessary. A brief incline in malaria during 2016 has raised fresh perturbation on whether elimination could be achieved on time or not. Conclusions The intervention tools available currently can most likely reduce transmission but clearing of malaria epicentres from where the disease can flare up any time, is not possible without involving local population. Nevertheless maintaining zero malaria transmission and checks on malaria import in declared malaria free countries, and further speeding up of interventions to stop transmission in elimination countries is most desirable. Strong collaboration backed by adequate political and financial support among the countries with a common objective to eliminate malaria must be on top priority. The present review attempts to assess the progress gained in malaria elimination during the past few years and highlights some issues that could be important in successful malaria elimination. Electronic supplementary material The online version of this article (10.1186/s40249-019-0524-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sunil Dhiman
- Vector Management Division, Defence Research and Development Establishment, Gwalior, Madhya Pradesh, 474002, India.
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44
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Kraemer MUG, Cummings DAT, Funk S, Reiner RC, Faria NR, Pybus OG, Cauchemez S. Reconstruction and prediction of viral disease epidemics. Epidemiol Infect 2018; 147:e34. [PMID: 30394230 PMCID: PMC6398585 DOI: 10.1017/s0950268818002881] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 08/24/2018] [Accepted: 09/21/2018] [Indexed: 01/29/2023] Open
Abstract
A growing number of infectious pathogens are spreading among geographic regions. Some pathogens that were previously not considered to pose a general threat to human health have emerged at regional and global scales, such as Zika and Ebola Virus Disease. Other pathogens, such as yellow fever virus, were previously thought to be under control but have recently re-emerged, causing new challenges to public health organisations. A wide array of new modelling techniques, aided by increased computing capabilities, novel diagnostic tools, and the increased speed and availability of genomic sequencing allow researchers to identify new pathogens more rapidly, assess the likelihood of geographic spread, and quantify the speed of human-to-human transmission. Despite some initial successes in predicting the spread of acute viral infections, the practicalities and sustainability of such approaches will need to be evaluated in the context of public health responses.
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Affiliation(s)
- M. U. G. Kraemer
- Harvard Medical School, Harvard University, Boston, MA, USA
- Computational Epidemiology Lab, Boston Children's Hospital, Boston, MA, USA
- Department of Zoology, University of Oxford, Oxford, UK
| | - D. A. T. Cummings
- Department of Biology, University of Florida, Gainesville, Florida, USA
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
| | - S. Funk
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, UK
- Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene & Tropical Medicine, London, UK
| | - R. C. Reiner
- Institute for Health Metrics and Evaluation, University of Washington, Seattle, USA
| | - N. R. Faria
- Department of Zoology, University of Oxford, Oxford, UK
| | - O. G. Pybus
- Department of Zoology, University of Oxford, Oxford, UK
| | - S. Cauchemez
- Mathematical Modelling of Infectious Diseases and Center of Bioinformatics, Biostatistics and Integrative Biology, Institut Pasteur, Paris, France
- CNRS UMR2000: Génomique évolutive, modélisation et santé, Paris, France
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45
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Ihantamalala FA, Herbreteau V, Rakotoarimanana FMJ, Rakotondramanga JM, Cauchemez S, Rahoilijaona B, Pennober G, Buckee CO, Rogier C, Metcalf CJE, Wesolowski A. Estimating sources and sinks of malaria parasites in Madagascar. Nat Commun 2018; 9:3897. [PMID: 30254280 PMCID: PMC6156502 DOI: 10.1038/s41467-018-06290-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2017] [Accepted: 08/21/2018] [Indexed: 02/03/2023] Open
Abstract
In areas where malaria epidemiology is spatially and temporally heterogeneous, human-mediated parasite importation can result in non-locally acquired clinical cases and outbreaks in low-transmission areas. Using mobility estimates derived from the mobile phone data and spatial malaria prevalence data, we identify travel routes relevant to malaria transmission in Madagascar. We find that the primary hubs of parasite importation are in a spatially connected area of the central highlands. Surprisingly, sources of these imported infections are not spatially clustered. We then related these source locations directly to clinical cases in the low-transmission area of the capital. We find that in the capital, a major sink, the primary sources of infection are along the more populated coastal areas, although these sources are seasonally variable. Our results have implications for targeting interventions at source locations to achieve local or national malaria control goals.
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Affiliation(s)
- Felana Angella Ihantamalala
- Institut Pasteur de Madagascar, 101 Antanarivo, Madagascar.,UMR 228 ESPACE-DEV (IRD, UM2, UR, UAG), Station SEAS-Ol, Saint-Pierre, Reunion, France
| | - Vincent Herbreteau
- UMR 228 ESPACE-DEV (IRD, UM2, UR, UAG), Station SEAS-Ol, Saint-Pierre, Reunion, France
| | | | | | - Simon Cauchemez
- Mathematical Modeling of Infectious Diseases Unit, Institut Pasteur, Paris, 75015, France.,Centre National de la Recherche Scientifique, URA3012, Paris, 75015, France.,Center of Bioinformatics, Biostatistics and Integrative Biology, Institut Pasteur, Paris, 75015, France
| | | | - Gwenaëlle Pennober
- UMR 228 ESPACE-DEV (IRD, UM2, UR, UAG), Station SEAS-Ol, Saint-Pierre, Reunion, France
| | - Caroline O Buckee
- Department of Epidemiology, Harvard School of Public Health, Boston, MA, 02115, USA.,Center for Communicable Disease Dynamics, Harvard School of Public Health, Boston, MA, 02115, USA
| | - Christophe Rogier
- Unité de recherche sur les maladies infectieuses et tropicales émergentes (URMITE), Paris, France.,Institute of Biomedical Research of the French Armed Forces (IRBA), Brétigny-Sur-Orge, France
| | - C J E Metcalf
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, 08540, USA.,Woodrow Wilson School of Public Affairs, Princeton University, Princeton, NJ, 08540, USA
| | - Amy Wesolowski
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21231, USA.
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46
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Cazelles B, Champagne C, Dureau J. Accounting for non-stationarity in epidemiology by embedding time-varying parameters in stochastic models. PLoS Comput Biol 2018; 14:e1006211. [PMID: 30110322 PMCID: PMC6110518 DOI: 10.1371/journal.pcbi.1006211] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2017] [Revised: 08/27/2018] [Accepted: 05/18/2018] [Indexed: 11/19/2022] Open
Abstract
The spread of disease through human populations is complex. The characteristics of disease propagation evolve with time, as a result of a multitude of environmental and anthropic factors, this non-stationarity is a key factor in this huge complexity. In the absence of appropriate external data sources, to correctly describe the disease propagation, we explore a flexible approach, based on stochastic models for the disease dynamics, and on diffusion processes for the parameter dynamics. Using such a diffusion process has the advantage of not requiring a specific mathematical function for the parameter dynamics. Coupled with particle MCMC, this approach allows us to reconstruct the time evolution of some key parameters (average transmission rate for instance). Thus, by capturing the time-varying nature of the different mechanisms involved in disease propagation, the epidemic can be described. Firstly we demonstrate the efficiency of this methodology on a toy model, where the parameters and the observation process are known. Applied then to real datasets, our methodology is able, based solely on simple stochastic models, to reconstruct complex epidemics, such as flu or dengue, over long time periods. Hence we demonstrate that time-varying parameters can improve the accuracy of model performances, and we suggest that our methodology can be used as a first step towards a better understanding of a complex epidemic, in situation where data is limited and/or uncertain.
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Affiliation(s)
- Bernard Cazelles
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS UMR 8197, Paris, France
- International Center for Mathematical and Computational Modeling of Complex Systems (UMMISCO), UMI 209, UPMC/IRD, France
- Hosts, Vectors and Infectious Agents, CNRS URA 3012, Institut Pasteur, Paris, France
| | - Clara Champagne
- Institut de Biologie de l’Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS UMR 8197, Paris, France
- CREST, ENSAE, Université Paris Saclay, Palaiseau, France
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47
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Routledge I, Chevéz JER, Cucunubá ZM, Rodriguez MG, Guinovart C, Gustafson KB, Schneider K, Walker PGT, Ghani AC, Bhatt S. Estimating spatiotemporally varying malaria reproduction numbers in a near elimination setting. Nat Commun 2018; 9:2476. [PMID: 29946060 PMCID: PMC6018772 DOI: 10.1038/s41467-018-04577-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 05/02/2018] [Indexed: 01/08/2023] Open
Abstract
In 2016 the World Health Organization identified 21 countries that could eliminate malaria by 2020. Monitoring progress towards this goal requires tracking ongoing transmission. Here we develop methods that estimate individual reproduction numbers and their variation through time and space. Individual reproduction numbers, Rc, describe the state of transmission at a point in time and differ from mean reproduction numbers, which are averages of the number of people infected by a typical case. We assess elimination progress in El Salvador using data for confirmed cases of malaria from 2010 to 2016. Our results demonstrate that whilst the average number of secondary malaria cases was below one (0.61, 95% CI 0.55–0.65), individual reproduction numbers often exceeded one. We estimate a decline in Rc between 2010 and 2016. However we also show that if importation is maintained at the same rate, the country may not achieve malaria elimination by 2020. Twenty one countries have been identified for malaria elimination by 2020 and their progress needs to be constantly evaluated. Here, the authors present a method that estimates individual reproduction numbers and their variation through time and space and use it to monitor elimination success in El Salvador between 2010 and 2016.
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Affiliation(s)
- Isobel Routledge
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG, UK.
| | | | - Zulma M Cucunubá
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG, UK
| | | | | | | | | | - Patrick G T Walker
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG, UK
| | - Azra C Ghani
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG, UK
| | - Samir Bhatt
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG, UK
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48
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Codeço CT, Villela DAM, Coelho FC. Estimating the effective reproduction number of dengue considering temperature-dependent generation intervals. Epidemics 2018; 25:101-111. [PMID: 29945778 DOI: 10.1016/j.epidem.2018.05.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Revised: 05/14/2018] [Accepted: 05/29/2018] [Indexed: 01/17/2023] Open
Abstract
The effective reproduction number, Rt, is a measure of transmission that can be calculated from standard incidence data to timely detect the beginning of epidemics. It has being increasingly used for surveillance of directly transmitted diseases. However, current methods for Rt estimation do not apply for vector borne diseases, whose transmission cycle depends on temperature. Here we propose a method that provides dengue's Rt estimates in the presence of temperature-mediated seasonality and apply this method to simulated and real data from two cities in Brazil where dengue is endemic. The method shows good precision in the simulated data. When applied to the real data, it shows differences in the transmission profile of the two cities and identifies periods of higher transmission.
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Affiliation(s)
- Claudia T Codeço
- Scientific Computing Program/Oswaldo Cruz Foundation, Rio de Janeiro, Brazil.
| | - Daniel A M Villela
- Scientific Computing Program/Oswaldo Cruz Foundation, Rio de Janeiro, Brazil
| | - Flavio C Coelho
- School of Applied Mathematics/Getulio Vargas Foundation, Rio de Janeiro, Brazil
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49
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Cohen JM, Le Menach A, Pothin E, Eisele TP, Gething PW, Eckhoff PA, Moonen B, Schapira A, Smith DL. Mapping multiple components of malaria risk for improved targeting of elimination interventions. Malar J 2017; 16:459. [PMID: 29132357 PMCID: PMC5683539 DOI: 10.1186/s12936-017-2106-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 11/02/2017] [Indexed: 11/13/2022] Open
Abstract
There is a long history of considering the constituent components of malaria risk and the malaria transmission cycle via the use of mathematical models, yet strategic planning in endemic countries tends not to take full advantage of available disease intelligence to tailor interventions. National malaria programmes typically make operational decisions about where to implement vector control and surveillance activities based upon simple categorizations of annual parasite incidence. With technological advances, an enormous opportunity exists to better target specific malaria interventions to the places where they will have greatest impact by mapping and evaluating metrics related to a variety of risk components, each of which describes a different facet of the transmission cycle. Here, these components and their implications for operational decision-making are reviewed. For each component, related mappable malaria metrics are also described which may be measured and evaluated by malaria programmes seeking to better understand the determinants of malaria risk. Implementing tailored programmes based on knowledge of the heterogeneous distribution of the drivers of malaria transmission rather than only consideration of traditional metrics such as case incidence has the potential to result in substantial improvements in decision-making. As programmes improve their ability to prioritize their available tools to the places where evidence suggests they will be most effective, elimination aspirations may become increasingly feasible.
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Affiliation(s)
- Justin M Cohen
- Clinton Health Access Initiative, 383 Dorchester Ave., Suite 400, Boston, MA, 02127, USA.
| | - Arnaud Le Menach
- Clinton Health Access Initiative, 383 Dorchester Ave., Suite 400, Boston, MA, 02127, USA
| | - Emilie Pothin
- Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
| | - Thomas P Eisele
- Center for Applied Malaria Research and Evaluation, Tulane University School of Public Health and Tropical Medicine, 1440 Canal St (2300), New Orleans, LA, 70112, USA
| | - Peter W Gething
- Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7LF, UK
| | - Philip A Eckhoff
- Institute for Disease Modeling, Building IV, 3150 139th Ave SE, Bellevue, WA, 98005, USA
| | - Bruno Moonen
- Bill & Melinda Gates Foundation, PO Box 23350, Seattle, WA, 98102, USA
| | | | - David L Smith
- Institute for Health Metrics and Evaluation, University of Washington, 2301 Fifth Ave., Suite 600, Seattle, WA, 98121, USA
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50
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Salje H, Lessler J, Maljkovic Berry I, Melendrez MC, Endy T, Kalayanarooj S, A-Nuegoonpipat A, Chanama S, Sangkijporn S, Klungthong C, Thaisomboonsuk B, Nisalak A, Gibbons RV, Iamsirithaworn S, Macareo LR, Yoon IK, Sangarsang A, Jarman RG, Cummings DAT. Dengue diversity across spatial and temporal scales: Local structure and the effect of host population size. Science 2017; 355:1302-1306. [PMID: 28336667 DOI: 10.1126/science.aaj9384] [Citation(s) in RCA: 98] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2016] [Revised: 12/15/2016] [Accepted: 02/16/2017] [Indexed: 12/30/2022]
Abstract
A fundamental mystery for dengue and other infectious pathogens is how observed patterns of cases relate to actual chains of individual transmission events. These pathways are intimately tied to the mechanisms by which strains interact and compete across spatial scales. Phylogeographic methods have been used to characterize pathogen dispersal at global and regional scales but have yielded few insights into the local spatiotemporal structure of endemic transmission. Using geolocated genotype (800 cases) and serotype (17,291 cases) data, we show that in Bangkok, Thailand, 60% of dengue cases living <200 meters apart come from the same transmission chain, as opposed to 3% of cases separated by 1 to 5 kilometers. At distances <200 meters from a case (encompassing an average of 1300 people in Bangkok), the effective number of chains is 1.7. This number rises by a factor of 7 for each 10-fold increase in the population of the "enclosed" region. This trend is observed regardless of whether population density or area increases, though increases in density over 7000 people per square kilometer do not lead to additional chains. Within Thailand these chains quickly mix, and by the next dengue season viral lineages are no longer highly spatially structured within the country. In contrast, viral flow to neighboring countries is limited. These findings are consistent with local, density-dependent transmission and implicate densely populated communities as key sources of viral diversity, with home location the focal point of transmission. These findings have important implications for targeted vector control and active surveillance.
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Affiliation(s)
- Henrik Salje
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA. .,Mathematical Modelling of Infectious Diseases Unit, Institut Pasteur, Paris, France.,CNRS, URA3012, Paris 75015, France.,Center of Bioinformatics, Biostatistics and Integrative Biology, Institut Pasteur, Paris 75015, France
| | - Justin Lessler
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
| | - Irina Maljkovic Berry
- Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, MD, 20910, USA
| | - Melanie C Melendrez
- Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, MD, 20910, USA
| | - Timothy Endy
- Department of Medicine, Upstate Medical University of New York, Syracuse, New York, NY, 13210, USA
| | | | | | - Sumalee Chanama
- National Institute of Health, Department of Medical Sciences, Nonthaburi, Thailand
| | - Somchai Sangkijporn
- National Institute of Health, Department of Medical Sciences, Nonthaburi, Thailand
| | - Chonticha Klungthong
- Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Butsaya Thaisomboonsuk
- Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Ananda Nisalak
- Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Robert V Gibbons
- Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | | | - Louis R Macareo
- Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - In-Kyu Yoon
- Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.,International Vaccine Institute, Seoul, South Korea
| | - Areerat Sangarsang
- National Institute of Health, Department of Medical Sciences, Nonthaburi, Thailand
| | - Richard G Jarman
- Viral Diseases Branch, Walter Reed Army Institute of Research, Silver Spring, MD, 20910, USA
| | - Derek A T Cummings
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA. .,Department of Biology, University of Florida, Gainesville, FL 32610, USA.,Emerging Pathogens Institute, University of Florida, Gainesville, FL 32610, USA
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