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Simon S, Amaku M, Massad E. Effects of migration rates and vaccination on the spread of yellow fever in Latin American communities. Rev Panam Salud Publica 2023; 47:e86. [PMID: 37266487 PMCID: PMC10231272 DOI: 10.26633/rpsp.2023.86] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 01/28/2023] [Indexed: 06/03/2023] Open
Abstract
Objective To assess how relevant the flow of people between communities is, compared to vaccination and type of vector, on the spread and potential outbreaks of yellow fever in a disease-free host community. Methods Using a SEIRV-SEI model for humans and vectors, we applied numerical simulations to the scenarios: (1) migration from an endemic community to a disease-free host community, comparing the performance of Haemagogus janthinomys and Aedes aegypti as vectors; (2) migration through a transit community located on a migratory route, where the disease is endemic, to a disease-free one; and (3) effects of different vaccination rates in the host community, considering the vaccination of migrants upon arrival. Results Results show no remarkable differences between scenarios 1 and 2. The type of vector and vaccination coverage in the host community are more relevant for the occurrence of outbreaks than migration rates, with H. janthinomys being more effective than A. aegypti. Conclusions With vaccination being more determinant for a potential outbreak than migration rates, vaccinating migrants on arrival may be one of the most effective measures against yellow fever. Furthermore, H. janthinomys is a more competent vector than A. aegypti at similar densities, but the presence of A. aegypti is a warning to maintain vaccination above recommended levels.
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Affiliation(s)
- Sabrina Simon
- University of São PauloSão PauloBrazilUniversity of São Paulo, São Paulo, Brazil
| | - Marcos Amaku
- University of São PauloSão PauloBrazilUniversity of São Paulo, São Paulo, Brazil
| | - Eduardo Massad
- Getúlio Vargas FoundationRio de JaneiroBrazilGetúlio Vargas Foundation, Rio de Janeiro, Brazil
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Poterek ML, Vogels CBF, Grubaugh ND, Ebel GD, Alex Perkins T, Cavany SM. Interactions between seasonal temperature variation and temporal synchrony drive increased arbovirus co-infection incidence. ROYAL SOCIETY OPEN SCIENCE 2022; 9:220829. [PMID: 36277835 PMCID: PMC9579765 DOI: 10.1098/rsos.220829] [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: 06/22/2022] [Accepted: 09/27/2022] [Indexed: 05/11/2023]
Abstract
Though instances of arthropod-borne (arbo)virus co-infection have been documented clinically, the overall incidence of arbovirus co-infection and its drivers are not well understood. Now that dengue, Zika and chikungunya viruses are all in circulation across tropical and subtropical regions of the Americas, it is important to understand the environmental and biological conditions that make co-infections more likely to occur. To understand this, we developed a mathematical model of co-circulation of two arboviruses, with transmission parameters approximating dengue, Zika and/or chikungunya viruses, and co-infection possible in both humans and mosquitoes. We examined the influence of seasonal timing of arbovirus co-circulation on the extent of co-infection. By undertaking a sensitivity analysis of this model, we examined how biological factors interact with seasonality to determine arbovirus co-infection transmission and prevalence. We found that temporal synchrony of the co-infecting viruses and average temperature were the most influential drivers of co-infection incidence. Our model highlights the synergistic effect of co-transmission from mosquitoes, which leads to more than double the number of co-infections than would be expected in a scenario without co-transmission. Our results suggest that appreciable numbers of co-infections are unlikely to occur except in tropical climates when the viruses co-occur in time and space.
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Affiliation(s)
- Marya L. Poterek
- Eck Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Chantal B. F. Vogels
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06510, USA
| | - Nathan D. Grubaugh
- Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06510, USA
| | - Gregory D. Ebel
- Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - T. Alex Perkins
- Eck Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Sean M. Cavany
- Eck Department of Biological Sciences and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556, USA
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Cracknell Daniels B, Gaythorpe K, Imai N, Dorigatti I. Yellow fever in Asia-a risk analysis. J Travel Med 2021; 28:taab015. [PMID: 33506250 PMCID: PMC8045179 DOI: 10.1093/jtm/taab015] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 01/19/2021] [Accepted: 01/20/2021] [Indexed: 12/30/2022]
Abstract
BACKGROUND There is concern about the risk of yellow fever (YF) establishment in Asia, owing to rising numbers of urban outbreaks in endemic countries and globalisation. Following an outbreak in Angola in 2016, YF cases were introduced into China. Prior to this, YF had never been recorded in Asia, despite climatic suitability and the presence of mosquitoes. An outbreak in Asia could result in widespread fatalities and huge economic impact. Therefore, quantifying the potential risk of YF outbreaks in Asia is a public health priority. METHODS Using international flight data and YF incidence estimates from 2016, we quantified the risk of YF introduction via air travel into Asia. In locations with evidence of a competent mosquito population, the potential for autochthonous YF transmission was estimated using a temperature-dependent model of the reproduction number and a branching process model assuming a negative binomial distribution. RESULTS In total, 25 cities across Asia were estimated to be at risk of receiving at least one YF viraemic traveller during 2016. At their average temperatures, we estimated the probability of autochthonous transmission to be <50% in all cities, which was primarily due to the limited number of estimated introductions that year. CONCLUSION Despite the rise in air travel, we found low support for travel patterns between YF endemic countries and Asia resulting in autochthonous transmission during 2016. This supports the historic absence of YF in Asia and suggests it could be due to a limited number of introductions in previous years. Future increases in travel volumes or YF incidence can increase the number of introductions and the risk of autochthonous transmission. Given the high proportion of asymptomatic or mild infections and the challenges of YF surveillance, our model can be used to estimate the introduction and outbreak risk and can provide useful information to surveillance systems.
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Affiliation(s)
- Bethan Cracknell Daniels
- MRC Centre for Global Infectious Disease Analysis; and the Abdul Latif Jameel Institute for Disease and Emergency Analytics (J-IDEA), School of Public Health, Imperial College London
| | - Katy Gaythorpe
- MRC Centre for Global Infectious Disease Analysis; and the Abdul Latif Jameel Institute for Disease and Emergency Analytics (J-IDEA), School of Public Health, Imperial College London
| | - Natsuko Imai
- MRC Centre for Global Infectious Disease Analysis; and the Abdul Latif Jameel Institute for Disease and Emergency Analytics (J-IDEA), School of Public Health, Imperial College London
| | - Ilaria Dorigatti
- MRC Centre for Global Infectious Disease Analysis; and the Abdul Latif Jameel Institute for Disease and Emergency Analytics (J-IDEA), School of Public Health, Imperial College London
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Lataillade LDGD, Vazeille M, Obadia T, Madec Y, Mousson L, Kamgang B, Chen CH, Failloux AB, Yen PS. Risk of yellow fever virus transmission in the Asia-Pacific region. Nat Commun 2020; 11:5801. [PMID: 33199712 PMCID: PMC7669885 DOI: 10.1038/s41467-020-19625-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Accepted: 10/22/2020] [Indexed: 02/07/2023] Open
Abstract
Historically endemic to Sub-Saharan Africa and South America, yellow fever is absent from the Asia-Pacific region. Yellow fever virus (YFV) is mainly transmitted by the anthropophilic Aedes mosquitoes whose distribution encompasses a large belt of tropical and sub tropical regions. Increasing exchanges between Africa and Asia have caused imported YFV incidents in non-endemic areas, which are threatening Asia with a new viral emergence. Here, using experimental infections of field-collected mosquitoes, we show that Asian-Pacific Aedes mosquitoes are competent vectors for YFV. We observe that Aedes aegypti populations from Singapore, Taiwan, Thailand, and New Caledonia are capable of transmitting YFV 14 days after oral infections, with a number of viral particles excreted from saliva reaching up to 23,000 viral particles. These findings represent the most comprehensive assessment of vector competence and show that Ae. aegypti mosquitoes from the Asia-Pacific region are highly competent to YFV, corroborating that vector populations are seemingly not a brake to the emergence of yellow fever in the region. Yellow fever is absent from the Asia/Pacific region, despite presence of the mosquito vector. Here, the authors demonstrate that mosquitoes collected from field sites across the region are capable of transmitting yellow fever virus, indicating that vector competence is not a barrier to disease spread.
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Affiliation(s)
| | - Marie Vazeille
- Arboviruses and Insect Vectors Unit, Institut Pasteur, Paris, France
| | - Thomas Obadia
- Bioinformatics and Biostatistics Hub, Institut Pasteur, USR 3756, CNRS, Paris, France.,Malaria Unit: Parasites and Hosts, Institut Pasteur, Paris, France
| | - Yoann Madec
- Emerging Diseases Epidemiology Unit, Institut Pasteur, Paris, France
| | - Laurence Mousson
- Arboviruses and Insect Vectors Unit, Institut Pasteur, Paris, France
| | - Basile Kamgang
- Department of Medical Entomology, Centre for Research in Infectious Diseases, Yaoundé, Cameroon
| | - Chun-Hong Chen
- National Health Research Institutes, Institute of Infectious Diseases and Vaccinology, Miaoli, Taiwan
| | | | - Pei-Shi Yen
- Arboviruses and Insect Vectors Unit, Institut Pasteur, Paris, France.
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Modeling and simulation of the spatial population dynamics of the Aedes aegypti mosquito with an insecticide application. Parasit Vectors 2020; 13:550. [PMID: 33160416 PMCID: PMC7648403 DOI: 10.1186/s13071-020-04426-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 10/24/2020] [Indexed: 11/10/2022] Open
Abstract
Background The Aedes aegypti mosquito is the primary vector for several diseases. Its control requires a better understanding of the mosquitoes’ live cycle, including the spatial dynamics. Several models address this issue. However, they rely on many hard to measure parameters. This work presents a model describing the spatial population dynamics of Aedes aegypti mosquitoes using partial differential equations (PDEs) relying on a few parameters. Methods We show how to estimate model parameter values from the experimental data found in the literature using concepts from dynamical systems, genetic algorithm optimization and partial differential equations. We show that our model reproduces some analytical formulas relating the carrying capacity coefficient to experimentally measurable quantities as the maximum number of mobile female mosquitoes, the maximum number of eggs, or the maximum number of larvae. As an application of the presented methodology, we replicate one field experiment numerically and investigate the effect of different frequencies in the insecticide application in the urban environment. Results The numerical results suggest that the insecticide application has a limited impact on the mosquitoes population and that the optimal application frequency is close to one week. Conclusions Models based on partial differential equations provide an efficient tool for simulating mosquitoes’ spatial population dynamics. The reduced model can reproduce such dynamics on a sufficiently large scale.![]()
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Disease Resurgence, Production Capability Issues and Safety Concerns in the Context of an Aging Population: Is There a Need for a New Yellow Fever Vaccine? Vaccines (Basel) 2019; 7:vaccines7040179. [PMID: 31717289 PMCID: PMC6963298 DOI: 10.3390/vaccines7040179] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 10/28/2019] [Accepted: 11/05/2019] [Indexed: 12/19/2022] Open
Abstract
Yellow fever is a potentially fatal, mosquito-borne viral disease that appears to be experiencing a resurgence in endemic areas in Africa and South America and spreading to non-endemic areas despite an effective vaccine. This trend has increased the level of concern about the disease and the potential for importation to areas in Asia with ecological conditions that can sustain yellow fever virus transmission. In this article, we provide a broad overview of yellow fever burden of disease, natural history, treatment, vaccine, prevention and control initiatives, and vaccine and therapeutic agent development efforts.
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Abstract
We present a model to optimise a vaccination campaign aiming to prevent or to curb a Zika virus outbreak. We show that the optimum vaccination strategy to reduce the number of cases by a mass vaccination campaign should start when the Aedes mosquitoes' density reaches the threshold of 1.5 mosquitoes per humans, the moment the reproduction number crosses one. The maximum time it is advisable to wait for the introduction of a vaccination campaign is when the first ZIKV case is identified, although this would not be as effective to minimise the number of infections as when the mosquitoes' density crosses the critical threshold. This suboptimum strategy, however, would still curb the outbreak. In both cases, the catch up strategy should aim to vaccinate at least 25% of the target population during a concentrated effort of 1 month immediately after identifying the threshold. This is the time taken to accumulate the herd immunity threshold of 56.5%. These calculations were done based on theoretical assumptions that vaccine implementation would be feasible within a very short time frame.
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Is vaccinating monkeys against yellow fever the ultimate solution for the Brazilian recurrent epizootics? Epidemiol Infect 2018; 146:1622-1624. [PMID: 30103835 DOI: 10.1017/s0950268818002273] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vaccinating monkeys against yellow fever (YF) has been a common practice in the beginning of the 17D vaccine development. Although it may seem strange at first sight, vaccinating monkeys as a public health strategy is, we think, feasible and theoretically could eliminate the infection among non-human primates, interrupting the virus circulation (or significantly reducing it) and therefore reducing the risk of spilling over to the human population. We propose a series of studies that could demonstrate (or not) the efficacy and feasibility of vaccinating non-human primates YF reservoirs living in green areas of urban centres to cut off or curb the virus circulation that recurrently spill over to the human population. Therefore, vaccinating monkeys in relatively small green areas of the urban centres is perhaps the ultimate solution for the Brazilian recurrent YF epizootics.
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Amaku M, Coutinho FAB, Armstrong M, Massad E. A Note on the Risk of Infections Invading Unaffected Regions. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2018; 2018:6289681. [PMID: 30073032 PMCID: PMC6057402 DOI: 10.1155/2018/6289681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 04/27/2018] [Accepted: 06/07/2018] [Indexed: 11/23/2022]
Abstract
We present two probabilistic models to estimate the risk of introducing infectious diseases into previously unaffected countries/regions by infective travellers. We analyse two distinct situations, one dealing with a directly transmitted infection (measles in Italy in 2017) and one dealing with a vector-borne infection (Zika virus in Rio de Janeiro, which may happen in the future). To calculate the risk in the first scenario, we used a simple, nonhomogeneous birth process. The second model proposed in this paper provides a way to calculate the probability that local mosquitoes become infected by the arrival of a single infective traveller during his/her infectiousness period. The result of the risk of measles invasion of Italy was of 93% and the result of the risk of Zika virus invasion of Rio de Janeiro was of 22%.
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Affiliation(s)
- Marcos Amaku
- School of Medicine, University of Sao Paulo, Sao Paulo, Brazil
| | | | - Margaret Armstrong
- School of Applied Mathematics, Fundação Getúlio Vargas, Rio de Janeiro, Brazil
| | - Eduardo Massad
- School of Medicine, University of Sao Paulo, Sao Paulo, Brazil
- School of Applied Mathematics, Fundação Getúlio Vargas, Rio de Janeiro, Brazil
- College of Natural and Life Sciences, The University of Derby, Derby, UK
- London School of Hygiene and Tropical Medicine, London, UK
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Abstract
Aedes aegypti, historically known as yellow fever (YF) mosquito, transmits a great number of other viruses such as Dengue, West Nile, Chikungunya, Zika, Mayaro and perhaps Oropouche, among others. Well established in Africa and Asia, Aedes mosquitoes are now increasingly invading large parts of the American continent, and hence the risk of urban YF resurgence in the American cities should because of great concern to public health authorities. Although no new urban cycle of YF was reported in the Americas since the end of an Aedes eradication programme in the late 1950s, the high number of non-vaccinated individuals that visit endemic areas, that is, South American jungles where the sylvatic cycle of YF is transmitted by canopy mosquitoes, and return to Aedes-infested urban areas, increases the risk of resurgence of the urban cycle of YF. We present a method to estimate the risk of urban YF resurgence in dengue-endemic cities. This method consists in (1) to estimate the number of Aedes mosquitoes that explains a given dengue outbreak in a given region; (2) calculate the force of infection caused by the introduction of one infective individual per unit area in the endemic area under study; (3) using the above estimates, calculate the probability of at least one autochthonous YF case per unit area produced by one single viraemic traveller per unit area arriving from a YF endemic or epidemic sylvatic region at the city studied. We demonstrate that, provided the relative vector competence, here defined as the capacity to being infected and disseminate the virus, of Ae. aegypti is greater than 0.7 (with respect to dengue), one infected traveller can introduce urban YF in a dengue endemic area.
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