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Dahlgren FS, Foppa IM, Stockwell MS, Vargas CY, LaRussa P, Reed C. Household transmission of influenza A and B within a prospective cohort during the 2013-2014 and 2014-2015 seasons. Stat Med 2021; 40:6260-6276. [PMID: 34580901 PMCID: PMC9293304 DOI: 10.1002/sim.9181] [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: 07/22/2021] [Accepted: 08/15/2021] [Indexed: 01/01/2023]
Abstract
People living within the same household as someone ill with influenza are at increased risk of infection. Here, we use Markov chain Monte Carlo methods to partition the hazard of influenza illness within a cohort into the hazard from the community and the hazard from the household. During the 2013‐2014 influenza season, 49 (4.7%) of the 1044 people enrolled in a community surveillance cohort had an acute respiratory illness (ARI) attributable to influenza. During the 2014‐2015 influenza season, 50 (4.7%) of the 1063 people in the cohort had an ARI attributable to influenza. The secondary attack rate from a household member was 2.3% for influenza A (H1) during 2013‐2014, 5.3% for influenza B during 2013‐2014, and 7.6% for influenza A (H3) during 2014‐2015. Living in a household with a person ill with influenza increased the risk of an ARI attributable to influenza up to 350%, depending on the season and the influenza virus circulating within the household.
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Affiliation(s)
- F Scott Dahlgren
- Influenza Division, Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Ivo M Foppa
- Influenza Division, Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.,Battelle Memorial Institute, Atlanta, Georgia, USA
| | - Melissa S Stockwell
- Division of Child and Adolescent Health, Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, USA.,Department of Population and Family Health, Mailman School of Public Health, Columbia University, New York, New York, USA
| | - Celibell Y Vargas
- Division of Child and Adolescent Health, Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, USA
| | - Philip LaRussa
- Division of Pediatric Infectious Diseases, Department of Pediatrics, College of Physicians and Surgeons, Columbia University, New York, New York, USA
| | - Carrie Reed
- Influenza Division, Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
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Yom-Tov E, Johansson-Cox I, Lampos V, Hayward AC. Estimating the secondary attack rate and serial interval of influenza-like illnesses using social media. Influenza Other Respir Viruses 2016; 9:191-9. [PMID: 25962320 PMCID: PMC4474495 DOI: 10.1111/irv.12321] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/30/2015] [Indexed: 12/05/2022] Open
Abstract
Objectives Knowledge of the secondary attack rate (SAR) and serial interval (SI) of influenza is important for assessing the severity of seasonal epidemics of the virus. To date, such estimates have required extensive surveys of target populations. Here, we propose a method for estimating the intrafamily SAR and SI from postings on the Twitter social network. This estimate is derived from a large number of people reporting ILI symptoms in them and\or their immediate family members. Design We analyze data from the 2012–2013 and the 2013–2014 influenza seasons in England and find that increases in the estimated SAR precede increases in ILI rates reported by physicians. Results We hypothesize that observed variations in the peak value of SAR are related to the appearance of specific strains of the virus and demonstrate this by comparing the changes in SAR values over time in relation to known virology. In addition, we estimate SI (the average time between cases) as 2·41 days for 2012 and 2·48 days for 2013. Conclusions The proposed method can assist health authorities by providing near-real-time estimation of SAR and SI, and especially in alerting to sudden increases thereof.
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Affiliation(s)
| | - Ingemar Johansson-Cox
- Department of Computer Science, University College London, London, UK.,Department of Computer Science, University of Copenhagen, Copenhagen, Denmark
| | - Vasileios Lampos
- Department of Computer Science, University College London, London, UK
| | - Andrew C Hayward
- Farr Institute of Health Informatics Research, University College London, London, UK
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Tsang TK, Lau LLH, Cauchemez S, Cowling BJ. Household Transmission of Influenza Virus. Trends Microbiol 2015; 24:123-133. [PMID: 26612500 PMCID: PMC4733423 DOI: 10.1016/j.tim.2015.10.012] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 10/05/2015] [Accepted: 10/28/2015] [Indexed: 12/13/2022]
Abstract
Human influenza viruses cause regular epidemics and occasional pandemics with a substantial public health burden. Household transmission studies have provided valuable information on the dynamics of influenza transmission. We reviewed published studies and found that once one household member is infected with influenza, the risk of infection in a household contact can be up to 38%, and the delay between onset in index and secondary cases is around 3 days. Younger age was associated with higher susceptibility. In the future, household transmission studies will provide information on transmission dynamics, including the correlation of virus shedding and symptoms with transmission, and the correlation of new measures of immunity with protection against infection. Historically, household cohort studies have provided valuable information on the incidence of respiratory infections and risk factors for infection. However, these studies require substantial resources and can provide limited information on transmission dynamics. Household transmission studies provide an efficient approach to describing the risk of influenza transmission and factors affecting transmission. In these studies, households with at least one member infected by influenza are eligible and are followed intensively for 1–2 weeks to observe secondary transmission within the household. Transmission studies also provide a model for evaluation of interventions in randomized controlled trials, and have been used to determine the efficacy of antiviral drugs for treatment and prophylaxis, and nonpharmaceutical interventions such as face masks and hand hygiene.
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Affiliation(s)
- Tim K Tsang
- WHO Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong Special Administrative Region, China
| | - Lincoln L H Lau
- Dalla Lana School of Public Health, University of Toronto, Toronto, Canada
| | - Simon Cauchemez
- Mathematical Modelling of Infectious Diseases Unit, Institut Pasteur, Paris, France
| | - Benjamin J Cowling
- WHO Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong Special Administrative Region, China.
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Okoli GN, Otete HE, Beck CR, Nguyen-Van-Tam JS. Use of neuraminidase inhibitors for rapid containment of influenza: a systematic review and meta-analysis of individual and household transmission studies. PLoS One 2014; 9:e113633. [PMID: 25490762 PMCID: PMC4260958 DOI: 10.1371/journal.pone.0113633] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Accepted: 10/29/2014] [Indexed: 11/18/2022] Open
Abstract
OBJECTIVES To assess the effectiveness of neuraminidase inhibitors for use in rapid containment of influenza. METHOD We conducted a systematic review and meta-analysis in accordance with the PRISMA statement. Healthcare databases and sources of grey literature were searched up to 2012 and records screened against protocol eligibility criteria. Data extraction and risk of bias assessments were performed using a piloted form. Results were synthesised narratively and we undertook meta-analyses to calculate pooled estimates of effect, statistical heterogeneity and assessed publication bias. FINDINGS Nine randomised controlled trials (RCTs) and eight observational studies met the inclusion criteria. Neuraminidase inhibitors provided 67 to 89% protection for individuals following prophylaxis. Meta-analysis of individual protection showed a significantly lower pooled odds of laboratory confirmed seasonal or influenza A(H1N1)pdm09 infection following oseltamivir usage compared to placebo or no therapy (n = 8 studies; odds ratio (OR) = 0.11; 95% confidence interval (CI) = 0.06 to 0.20; p<0.001; I2 = 58.7%). This result was comparable to the pooled odds ratio for individual protection with zanamivir (OR = 0.23; 95% CI 0.16 to 0.35). Similar point estimates were obtained with widely overlapping 95% CIs for household protection with oseltamivir or zanamivir. We found no studies of neuraminidase inhibitors to prevent population-wide community transmission of influenza. CONCLUSION Oseltamivir and zanamivir are effective for prophylaxis of individuals and households irrespective of treatment of the index case. There are no data which directly support an effect on wider community transmission. PROTOCOL REGISTRY PROSPERO registration number: CRD42013003880.
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Affiliation(s)
- George N. Okoli
- Division of Epidemiology and Public Health, University of Nottingham, Nottingham, England, United Kingdom
| | - Harmony E. Otete
- Division of Epidemiology and Public Health, University of Nottingham, Nottingham, England, United Kingdom
| | - Charles R. Beck
- Division of Epidemiology and Public Health, University of Nottingham, Nottingham, England, United Kingdom
| | - Jonathan S. Nguyen-Van-Tam
- Division of Epidemiology and Public Health, University of Nottingham, Nottingham, England, United Kingdom
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Khuntirat B, Yoon IK, Chittaganpitch M, Krueger WS, Supawat K, Blair PJ, Putnam SD, Gibbons RV, Buddhari D, Sawanpanyalert P, Heil GL, Friary JA, Gray GC. High rate of A(H1N1)pdm09 infections among rural Thai villagers, 2009-2010. PLoS One 2014; 9:e106751. [PMID: 25188434 PMCID: PMC4154756 DOI: 10.1371/journal.pone.0106751] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 08/09/2014] [Indexed: 11/18/2022] Open
Abstract
Background Pandemic influenza A(H1N1)pdm09 emerged in Thailand in 2009. A prospective longitudinal adult cohort and household transmission study of influenza-like illness (ILI) was ongoing in rural Thailand at the time of emergence. Symptomatic and subclinical A(H1N1)pdm09 infection rates in the cohort and among household members were evaluated. Methods A cohort of 800 Thai adults underwent active community-based surveillance for ILI from 2008–2010. Acute respiratory samples from ILI episodes were tested for A(H1N1)pdm09 by qRT-PCR; acute and 60-day convalescent blood samples were tested by A(H1N1)pdm09 hemagglutination inhibition assay (HI). Enrollment, 12-month and 24-month follow-up blood samples were tested for A(H1N1)pdm09 seroconversion by HI. Household members of influenza A-infected cohort subjects with ILI were enrolled in household transmission investigations in which day 0 and 60 blood samples and acute respiratory samples were tested by either qRT-PCR or HI for A(H1N1)pdm09. Seroconversion between annual blood samples without A(H1N1)pdm09-positive ILI was considered as subclinical infection. Results The 2-yr cumulative incidence of A(H1N1)pdm09 infection in the cohort in 2009/2010 was 10.8% (84/781) with an annual incidence of 1.2% in 2009 and 9.7% in 2010; 83.3% of infections were subclinical (50% in 2009 and 85.9% in 2010). The 2-yr cumulative incidence was lowest (5%) in adults born ≤1957. The A(H1N1)pdm09 secondary attack rate among household contacts was 47.2% (17/36); 47.1% of these infections were subclinical. The highest A(H1N1)pdm09 secondary attack rate among household contacts (70.6%, 12/17) occurred among children born between 1990 and 2003. Conclusion Subclinical A(H1N1)pdm09 infections in Thai adults occurred frequently and accounted for a greater proportion of all A(H1N1)pdm09 infections than previously estimated. The role of subclinical infections in A(H1N1)pdm09 transmission has important implications in formulating strategies to predict and prevent the spread of A(H1N1)pdm09 and other influenza virus strains.
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Affiliation(s)
- Benjawan Khuntirat
- 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
| | | | - Whitney S. Krueger
- College of Public Health and Health Professions and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - Krongkaew Supawat
- National Institute of Health, Ministry of Public Health, Nonthaburi, Thailand
| | | | - Shannon D. Putnam
- Naval Health Research Center, San Diego, California, United States of America
| | - Robert V. Gibbons
- Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | - Darunee Buddhari
- Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand
| | | | - Gary L. Heil
- College of Public Health and Health Professions and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - John A. Friary
- College of Public Health and Health Professions and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
| | - Gregory C. Gray
- College of Public Health and Health Professions and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, United States of America
- * E-mail:
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Beck CR, Sokal R, Arunachalam N, Puleston R, Cichowska A, Kessel A, Zambon M, Nguyen-Van-Tam JS. Neuraminidase inhibitors for influenza: a review and public health perspective in the aftermath of the 2009 pandemic. Influenza Other Respir Viruses 2013; 7 Suppl 1:14-24. [PMID: 23279893 DOI: 10.1111/irv.12048] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
OBJECTIVES The objectives of this study were to: (1) reflect on key stages in the discovery, development and pre-pandemic use of neuraminidase inhibitors (NAIs), (2) summarise the evidence of NAI effectiveness for treatment and prophylaxis of seasonal influenza prior to the 2009 pandemic, and (3) summarise the evidence base generated during the 2009 pandemic period. DESIGN A rapid systematic review of evidence published to June 2010 was conducted where existing high-quality systematic reviews formed a baseline and were supplemented with data from other reviews, randomised controlled trials (RCTs) and observational studies. MAIN OUTCOME MEASURES Severity and duration of symptoms; rates of severe illness, complications and death following treatment for influenza or influenza-like illness; rates of influenza and influenza-like illness following long-term prophylaxis or post-exposure prophylaxis of household contacts. RESULTS Prior to the 2009 pandemic, evidence from RCTs conducted in seasonal influenza epidemics indicated that NAIs used to treat laboratory-confirmed influenza in healthy adults reduced the duration of illness by one day. NAIs provide high levels of protective efficacy in adults when given long-term or in household-based post-exposure prophylaxis for seasonal influenza. Several 2009 pandemic period observational studies suggest that early treatment may reduce rates of hospitalisation and in-hospital mortality, but data from that period do not substantially increase the evidence base on prophylaxis, although they confirm effectiveness. CONCLUSIONS NAIs should be deployed during a future pandemic for either post-exposure prophylaxis or treatment depending on national policy considerations and logistics. The existing evidence base on effectiveness against severe outcomes requires supplementation.
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Affiliation(s)
- Charles R Beck
- Health Protection and Influenza Research Group, Division of Epidemiology and Public Health, School of Community Health Sciences, University of Nottingham, Nottingham, UK
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Mizumoto K, Nishiura H, Yamamoto T. Effectiveness of antiviral prophylaxis coupled with contact tracing in reducing the transmission of the influenza A (H1N1-2009): a systematic review. Theor Biol Med Model 2013; 10:4. [PMID: 23324555 PMCID: PMC3563494 DOI: 10.1186/1742-4682-10-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 01/14/2013] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND During the very early stage of the 2009 pandemic, mass chemoprophylaxis was implemented as part of containment measure. The purposes of the present study were to systematically review the retrospective studies that investigated the effectiveness of antiviral prophylaxis during the 2009 pandemic, and to explicitly estimate the effectiveness by employing a mathematical model. METHODS A systematic review identified 17 articles that clearly defined the cases and identified exposed individuals based on contact tracing. Analysing a specific school-driven outbreak, we estimated the effectiveness of antiviral prophylaxis using a renewal equation model. Other parameters, including the reproduction number and the effectiveness of antiviral treatment and school closure, were jointly estimated. RESULTS Based on the systematic review, median secondary infection risks (SIRs) among exposed individuals with and without prophylaxis were estimated at 2.1% (quartile: 0, 12.2) and 16.6% (quartile: 8.4, 32.4), respectively. A very high heterogeneity in the SIR was identified with an estimated I2 statistic at 71.8%. From the outbreak data in Madagascar, the effectiveness of mass chemoprophylaxis in reducing secondary transmissions was estimated to range from 92.8% to 95.4% according to different model assumptions and likelihood functions, not varying substantially as compared to other parameters. CONCLUSIONS Only based on the meta-analysis of retrospective studies with different study designs and exposure settings, it was not feasible to estimate the effectiveness of antiviral prophylaxis in reducing transmission. However, modelling analysis of a single outbreak successfully yielded an estimate of the effectiveness that appeared to be robust to model assumptions. Future studies should fill the data gap that has existed in observational studies and allow mathematical models to be used for the analysis of meta-data.
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Affiliation(s)
- Kenji Mizumoto
- School of Public Health, The University of Hong Kong, 100 Cyberport Road, Pokfulam, Hong Kong, China
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Zhang L, Peng Z, Ou J, Zeng G, Fontaine RE, Liu M, Cui F, Hong R, Zhou H, Huai Y, Chuang SK, Leung YH, Feng Y, Luo Y, Shen T, Zhu BP, Widdowson MA, Yu H. Protection by face masks against influenza A(H1N1)pdm09 virus on trans-Pacific passenger aircraft, 2009. Emerg Infect Dis 2013; 19. [PMID: 23968983 PMCID: PMC3810906 DOI: 10.3201/eid1909.121765] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
In response to several influenza A(H1N1)pdm09 infections that developed in passengers after they traveled on the same 2 flights from New York, New York, USA, to Hong Kong, China, to Fuzhou, China, we assessed transmission of influenza A(H1N1)pdm09 virus on these flights. We defined a case of infection as onset of fever and respiratory symptoms and detection of virus by PCR in a passenger or crew member of either flight. Illness developed only in passengers who traveled on the New York to Hong Kong flight. We compared exposures of 9 case-passengers with those of 32 asymptomatic control-passengers. None of the 9 case-passengers, compared with 47% (15/32) of control-passengers, wore a face mask for the entire flight (odds ratio 0, 95% CI 0-0.71). The source case-passenger was not identified. Wearing a face mask was a protective factor against influenza infection. We recommend a more comprehensive intervention study to accurately estimate this effect.
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Affiliation(s)
- Lijie Zhang
- Chinese Center for Disease Control and Prevention, Beijing, China
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Archer BN, Tempia S, White LF, Pagano M, Cohen C. Reproductive number and serial interval of the first wave of influenza A(H1N1)pdm09 virus in South Africa. PLoS One 2012; 7:e49482. [PMID: 23166682 PMCID: PMC3500305 DOI: 10.1371/journal.pone.0049482] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 10/09/2012] [Indexed: 11/19/2022] Open
Abstract
Background/Objective Describing transmissibility parameters of past pandemics from diverse geographic sites remains critical to planning responses to future outbreaks. We characterize the transmissibility of influenza A(H1N1)pdm09 (hereafter pH1N1) in South Africa during 2009 by estimating the serial interval (SI), the initial effective reproductive number (initial Rt) and the temporal variation of Rt. Methods We make use of data from a central registry of all pH1N1 laboratory-confirmed cases detected throughout South Africa. Whenever date of symptom onset is missing, we estimate it from the date of specimen collection using a multiple imputation approach repeated 100 times for each missing value. We apply a likelihood-based method (method 1) for simultaneous estimation of initial Rt and the SI; estimate initial Rt from SI distributions established from prior field studies (method 2); and the Wallinga and Teunis method (method 3) to model the temporal variation of Rt. Results 12,360 confirmed pH1N1 cases were reported in the central registry. During the period of exponential growth of the epidemic (June 21 to August 3, 2009), we simultaneously estimate a mean Rt of 1.47 (95% CI: 1.30–1.72) and mean SI of 2.78 days (95% CI: 1.80–3.75) (method 1). Field studies found a mean SI of 2.3 days between primary cases and laboratory-confirmed secondary cases, and 2.7 days when considering both suspected and confirmed secondary cases. Incorporating the SI estimate from field studies using laboratory-confirmed cases, we found an initial Rt of 1.43 (95% CI: 1.38–1.49) (method 2). The mean Rt peaked at 2.91 (95% CI: 0.85–2.91) on June 21, as the epidemic commenced, and Rt>1 was sustained until August 22 (method 3). Conclusions Transmissibility characteristics of pH1N1 in South Africa are similar to estimates reported by countries outside of Africa. Estimations using the likelihood-based method are in agreement with field findings.
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Affiliation(s)
- Brett N. Archer
- National Institute for Communicable Diseases (NICD), National Health Laboratory Service (NHLS), Johannesburg, Gauteng, South Africa
| | - Stefano Tempia
- United States Centers for Disease Control and Prevention, Attaché to the National Institute for Communicable Diseases (NICD), National Health Laboratory Service (NHLS), Johannesburg, Gauteng, South Africa
| | - Laura F. White
- Department of Biostatistics, School of Public Health, Boston University, Boston, Massachusetts, United States of America
| | - Marcello Pagano
- School of Public Health, Harvard University, Cambridge, Massachusetts, United States of America
| | - Cheryl Cohen
- National Institute for Communicable Diseases (NICD), National Health Laboratory Service (NHLS), Johannesburg, Gauteng, South Africa
- School of Public Health, University of Witwatersrand, Johannesburg, Gauteng, South Africa
- * E-mail:
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Cheng VCC, To KKW, Tse H, Hung IFN, Yuen KY. Two years after pandemic influenza A/2009/H1N1: what have we learned? Clin Microbiol Rev 2012; 25:223-63. [PMID: 22491771 PMCID: PMC3346300 DOI: 10.1128/cmr.05012-11] [Citation(s) in RCA: 154] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The world had been anticipating another influenza pandemic since the last one in 1968. The pandemic influenza A H1N1 2009 virus (A/2009/H1N1) finally arrived, causing the first pandemic influenza of the new millennium, which has affected over 214 countries and caused over 18,449 deaths. Because of the persistent threat from the A/H5N1 virus since 1997 and the outbreak of the severe acute respiratory syndrome (SARS) coronavirus in 2003, medical and scientific communities have been more prepared in mindset and infrastructure. This preparedness has allowed for rapid and effective research on the epidemiological, clinical, pathological, immunological, virological, and other basic scientific aspects of the disease, with impacts on its control. A PubMed search using the keywords "pandemic influenza virus H1N1 2009" yielded over 2,500 publications, which markedly exceeded the number published on previous pandemics. Only representative works with relevance to clinical microbiology and infectious diseases are reviewed in this article. A significant increase in the understanding of this virus and the disease within such a short amount of time has allowed for the timely development of diagnostic tests, treatments, and preventive measures. These findings could prove useful for future randomized controlled clinical trials and the epidemiological control of future pandemics.
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Affiliation(s)
- Vincent C C Cheng
- Department of Microbiology, Queen Mary Hospital, Hong Kong Special Administrative Region, China
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11
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Janjua NZ, Skowronski DM, Hottes TS, Osei W, Adams E, Petric M, Lem M, Tang P, De Serres G, Patrick DM, Bowering D. Transmission dynamics and risk factors for pandemic H1N1-related illness: outbreak investigation in a rural community of British Columbia, Canada. Influenza Other Respir Viruses 2012; 6:e54-62. [PMID: 22385647 PMCID: PMC4986582 DOI: 10.1111/j.1750-2659.2012.00344.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
OBJECTIVE To characterize the first-wave epidemiologic features of influenza-like illness (ILI) associated with the novel pandemic A/H1N1 [A(H1N1)pdm09] virus. METHODS We used generalized linear mixed models (GLMM) to assess risk factors and non-parametric and/or parametric distributions to estimate attack rates, secondary attack rates (SAR), duration of illness, and serial interval during a laboratory-confirmed community outbreak of A(H1N1)pdm09 clustered around on-reserve residents and households of an elementary school in rural British Columbia, Canada, in late April/early May 2009. ILI details were collected as part of outbreak investigation by community telephone survey in early June 2009. RESULTS Overall, 92/408 (23%) of participants developed ILI and 36/408 (9%) experienced medically attended ILI (MAILI). The overall SAR in households was 22%: highest among participants 1-4 years of age (yoa) (50%) followed by < 1 yoa (38%), 5-8 yoa (20%), 10-19 yoa (13%), 20-49 yoa (20%), and 50-64 yoa (0%). The median serial interval was estimated at 3·5 days (95% CI: 2·1-5·1). In multivariable GLMM analysis, having a chronic condition (OR: 2·58; 95% CI: 1·1-6·04), younger age [1-8 yoa: OR: 4·63; 95% CI: 2·25-9·52; 9-19 yoa: OR: 1·95; 95% CI: 0·97-3·9 (referent: ≥ 20 yoa)] and receipt of 2008-2009 influenza vaccine (OR: 2·68; 95% CI: 1·37-5·25) were associated with increased risk of ILI. Median duration of illness was 9 days, longer among those with chronic conditions (21 days). Median time to seeking care after developing illness was 4·5 days. On-reserve participants had higher chronic conditions, household density, ILI, MAILI, and SAR. CONCLUSIONS During a community outbreak of A(H1N1)pdm09-related illness, we identified substantial clinical ILI attack rates exceeding 20% with secondary household attack rates as high as 50% in young children. The serial interval was short suggesting a narrow period to prevent transmission.
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Mohamed AG, BinSaeed AA, Al-Habib H, Al-Saif H. Communicability of H1N1 and seasonal influenza among household contacts of cases in large families. Influenza Other Respir Viruses 2011; 6:e25-9. [PMID: 22118477 PMCID: PMC4941675 DOI: 10.1111/j.1750-2659.2011.00308.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Please cite this paper as: Mohamed et al. (2011) Communicability of H1N1 and seasonal influenza among household contacts of cases in large families. Influenza and Other Respiratory Viruses 6(3), e25–e29. Background Quantitative knowledge of the transmissibility of influenza is crucial to its prevention and control. Objectives To quantify the transmission of influenza A (H1N1) and seasonal influenza in household contacts of patients with influenza diagnosed in a large university hospital. Patients/Methods A prospective study was conducted between September and October 2009 in which all confirmed cases of influenza diagnosed at King Khalid University Hospital were included. All household contacts were followed by telephone calls every other day for 12 days. They were asked about the development of influenza symptoms in addition to their age and nationality. Results Overall, 432 household contacts of 69 influenza A (H1N1) cases and 417 contacts of 91 seasonal influenza cases were included. Suspected influenza was diagnosed in 16·9% and 14·4% of household contacts of H1N1 and seasonal influenza patients, respectively. Household reproduction numbers were 1·06 (0·84–1·28) for H1N1 and 0·66 (0·51–0·81) for seasonal influenza. Children in households were more susceptible than were adults (22·2% versus 13·7%, respectively). Evidence of coughing in the index case tripled the risk of infection in households afflicted with the H1N1 influenza [relative risk (RR) = 3·28, CI = 1·24–8·69], while evidence of a runny nose doubled it (RR = 1·89, CI = 1·19–2·92). Conclusions Communicability of influenza in households in Riyadh is comparable to that in other countries. Children are more susceptible to influenza infection. The presence of a cough or runny nose in the index cases increases the risk of infection.
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Affiliation(s)
- Ashry G Mohamed
- Department of Family and Community Medicine, College of Medicine, King Saud University, Riyadh, Saudi Arabia.
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Pebody RG, Harris R, Kafatos G, Chamberland M, Campbell C, Nguyen-Van-Tam JS, McLean E, Andrews N, White PJ, Wynne-Evans E, Green J, Ellis J, Wreghitt T, Bracebridge S, Ihekweazu C, Oliver I, Smith G, Hawkins C, Salmon R, Smyth B, McMenamin J, Zambon M, Phin N, Watson JM. Use of Antiviral Drugs to Reduce Household Transmission of Pandemic (H1N1) 2009, United Kingdom1. Emerg Infect Dis 2011; 17:990-9. [DOI: 10.3201/eid/1706.101161] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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Ninomiya-Mori A, Nukuzuma S, Suga T, Akiyoshi K, Nukina M, Tanaka T. Genetic evidence for containment of viruses in the first outbreak of influenza A pandemic (H1N1) 2009 in Kobe, Japan. Influenza Other Respir Viruses 2011; 5:180-7. [PMID: 21477137 PMCID: PMC4941588 DOI: 10.1111/j.1750-2659.2010.00188.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Please cite this paper as: Ninomiya‐Mori et al. (2010) Genetic evidence for containment of viruses in the first outbreak of influenza A pandemic (H1N1) 2009 in Kobe, Japan. Influenza and Other Respiratory Viruses Doi: 10.1111/j.1750‐2659.2010.00188.x. Background On 16 May 2009, a high school student in Kobe with no history of overseas travel was reported as the first case of influenza A pandemic (H1N1) 2009 virus infection in Japan. Subsequently, it was revealed that the infection had spread to some cities in the Kansai region and most patients were high school students. The number of patients decreased rapidly within a week; however, it began to increase in the middle of July. Methods We phylogenetically analyzed viral characteristics using 27 viruses isolated from patients living in Kobe. Results and conclusions We demonstrated that viruses isolated in the early phase of the outbreak were distinguishable from those after the reappearance of patients. These findings provide genetic evidence for the effectiveness of public health containment measures in the Kansai region in preventing the progression of the outbreak.
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Fierro A, Liccardo A. A simple stochastic lattice gas model for H1N1 pandemic. Application to the Italian epidemiological data. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2011; 34:11. [PMID: 21337015 DOI: 10.1140/epje/i2011-11011-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Accepted: 01/20/2011] [Indexed: 05/30/2023]
Abstract
We construct a very simple epidemic model for influenza spreading in an age-class-distributed population, by coupling a lattice gas model for the population dynamics with a SIR stochastic model for susceptible, infected and removed/immune individuals. We use as a test case the age-distributed Italian epidemiological data for the novel influenza A(H1N1). The most valuable features of this model are its country-independent and virus-independent structure (few demographic, social and virological data are used to fix some parameters), its large statistic due to a very short run-time machine, and its easy generalizability to include mitigation strategies. In spite of its simplicity, the model presented reproduces the epidemiological Italian data, with sensible predictions for the reproduction number and theoretically interesting results for the generation time distribution.
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Affiliation(s)
- A Fierro
- CNR-SPIN, via Cinthia, 80126, Napoli, Italy.
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Estimating time to onset of swine influenza symptoms after initial novel A(H1N1v) viral infection. Epidemiol Infect 2010; 139:1418-24. [DOI: 10.1017/s0950268810002566] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
SUMMARYCharacterization of the incubation time from infection to onset is important for understanding the natural history of infectious diseases. Attempts to estimate the incubation time distribution for novel A(H1N1v) have been, up to now, based on limited data or peculiar samples. We characterized this distribution for a generic group of symptomatic cases using laboratory-confirmed swine influenza case-information. Estimates of the incubation distribution for the pandemic influenza were derived through parametric time-to-event analyses of data on onset of symptoms and exposure dates, accounting for interval censoring. We estimated a mean of about 1·6–1·7 days with a standard deviation of 2 days for the incubation time distribution in those who became symptomatic after infection with the A(H1N1v) virus strain. Separate analyses for the <15 years and ⩾15 years age groups showed a significant (P<0·02) difference with a longer mean incubation time in the older age group.
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Liu SL, Zhang ZR, Wang C, Dong Y, Cui LB, Yang XH, Sun Z, Wang J, Chen J, Huang RJ, Miao F, Ruan B, Xie L, He HX, Deng J. 2009 pandemic characteristics and controlling experiences of influenza H1N1 virus 1 year after the inception in Hangzhou, China. J Med Virol 2010; 82:1985-95. [DOI: 10.1002/jmv.21964] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Transmission of pandemic influenza A (H1N1) 2009 within households: Edmonton, Canada. J Clin Virol 2010; 49:90-3. [PMID: 20673645 DOI: 10.1016/j.jcv.2010.06.015] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Revised: 06/12/2010] [Accepted: 06/29/2010] [Indexed: 11/23/2022]
Abstract
BACKGROUND In April 2009, a novel influenza A, subtype H1N1, now referred to as the Pandemic (H1N1) 2009 virus (pH1N1), began circulating in countries around the world. Describing the transmission characteristics of this novel influenza A virus is important to predict current, and future, disease spread. The Public Health response to the first wave of pH1N1 in Alberta focused on the identification and management of secondary cases within households. OBJECTIVES The purpose of this study was to describe transmission characteristics of pH1N1 in households in Edmonton, the capital city of Alberta, during the first wave, and to identify the serial interval and secondary attack rate (SAR) in this setting. STUDY DESIGN This is a prospective analysis of pH1N1 household transmission within 87 urban Canadian households between April 30 and June 9, 2009; with each household having at least one laboratory-confirmed case. The secondary attack rate was calculated in the 262 household contacts using a weighted average by number of susceptible individuals in each household. The serial interval, or time to illness in secondary cases, was analyzed using survival analysis with a Weibull model. RESULTS Within the 87 households, 42 (48.3%) had no secondary cases develop; 25 (28.7%) had one secondary case develop; and 20 (22.9%) had more than one secondary case develop. The secondary attack rate did not decrease with increasing household size and households with two members exhibited the lowest secondary attack rate at 14.1%. Children under the age of 19, and individuals with an underlying medical condition, were at increased risk (p<0.05) of becoming a secondary case. The overall secondary attack rate among the 262 susceptible household contacts was 30.2% (95% CI: 12.6-52.2). The median serial interval for pH1N1 transmission was 3.4 days (95% CI: 2.9-3.9). CONCLUSIONS The identified transmission characteristics of pH1N1 among Canadian households differ slightly from other previously reported North American estimates, but are in keeping with historical transmission rates of pandemic influenza viruses.
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van Boven M, Donker T, van der Lubben M, van Gageldonk-Lafeber RB, te Beest DE, Koopmans M, Meijer A, Timen A, Swaan C, Dalhuijsen A, Hahné S, van den Hoek A, Teunis P, van der Sande MAB, Wallinga J. Transmission of novel influenza A(H1N1) in households with post-exposure antiviral prophylaxis. PLoS One 2010; 5:e11442. [PMID: 20628642 PMCID: PMC2898802 DOI: 10.1371/journal.pone.0011442] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2009] [Accepted: 05/26/2010] [Indexed: 11/19/2022] Open
Abstract
Background Despite impressive advances in our understanding of the biology of novel influenza A(H1N1) virus, little is as yet known about its transmission efficiency in close contact places such as households, schools, and workplaces. These are widely believed to be key in supporting propagating spread, and it is therefore of importance to assess the transmission levels of the virus in such settings. Methodology/Principal Findings We estimate the transmissibility of novel influenza A(H1N1) in 47 households in the Netherlands using stochastic epidemic models. All households contained a laboratory confirmed index case, and antiviral drugs (oseltamivir) were given to both the index case and other households members within 24 hours after detection of the index case. Among the 109 household contacts there were 9 secondary infections in 7 households. The overall estimated secondary attack rate is low (0.075, 95%CI: 0.037–0.13). There is statistical evidence indicating that older persons are less susceptible to infection than younger persons (relative susceptibility of older persons: 0.11, 95%CI: 0.024–0.43. Notably, the secondary attack rate from an older to a younger person is 0.35 (95%CI: 0.14–0.61) when using an age classification of ≤12 versus >12 years, and 0.28 (95%CI: 0.12–0.50) when using an age classification of ≤18 versus >18 years. Conclusions/Significance Our results indicate that the overall household transmission levels of novel influenza A(H1N1) in antiviral-treated households were low in the early stage of the epidemic. The relatively high rate of adult-to-child transmission indicates that control measures focused on this transmission route will be most effective in minimizing the total number of infections.
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Affiliation(s)
- Michiel van Boven
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
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A school outbreak of pandemic (H1N1) 2009 infection: assessment of secondary household transmission and the protective role of oseltamivir. Epidemiol Infect 2010; 139:41-4. [DOI: 10.1017/s0950268810001445] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
SUMMARYIn mid-June 2009, an outbreak of pandemic (H1N1) 2009 (pH1N1) infection occurred in a secondary school in Hong Kong. We carried out an epidemiological investigation to delineate the characteristics of the outbreak, gauge the extent of secondary household transmission, and assess the protective role of oseltamivir in household contacts. We interviewed pH1N1-confirmed cases using a standardized questionnaire. Sixty-five of 511 students in the school were affected. Of the 205 household contacts identified, 12 were confirmed as cases. All cases recovered. The estimated secondary household attack rate was 5·9% (95% CI 2·7–9·1). Household contacts aged <18 years were about 15 times more likely to be infected than older contacts. Household contacts who had received oseltamivir prophylaxis were less likely to acquire a secondary infection than those who had not (odds ratio=0). The estimated mean household serial interval of pH1N1 virus was 2·8 days (95% CI 2·1–3·4 days).
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Low secondary transmission of 2009 pandemic influenza A (H1N1) in households following an outbreak at a summer camp: relationship to timing of exposure. Epidemiol Infect 2010; 139:45-51. [DOI: 10.1017/s095026881000141x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SUMMARYFollowing an outbreak of 2009 pandemic influenza A (H1N1) at a residential summer camp for boys aged 10–16 years, we assessed secondary household transmission of the novel virus after their return home. Of 212 study participants who attended camp, 49 had confirmed or probable influenza for a primary attack rate of 23%. Of 87 exposed household contacts who did not attend camp, only three instances of probable transmission were observed, for a household secondary attack rate of 3·5%. All secondary cases occurred in households where the ill camp attendee returned home 1 day after onset of illness, with an attack rate of 14·3% in household contacts in this category. Returning home after peak infectivity to others and advanced warning prior to reintegration of sick individuals into the household probably contributed to the overall low secondary attack rate observed.
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Chan M, Chen MI, Chow A, Lee CPS, Tan ASH, Lye DC, Leo YS. Pandemic (H1N1) 2009: Clinical and Laboratory Findings of the First Fifty Cases in Singapore. ANNALS OF THE ACADEMY OF MEDICINE, SINGAPORE 2010. [DOI: 10.47102/annals-acadmedsg.v39n4p267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Introduction: Since the first imported case on 26 May 2009, pandemic (H1N1) 2009 has spread from travellers and has resulted in sustained community transmission. Singapore began with a strict containment policy where all suspected and confirmed cases of pandemic (H1N1) 2009 were admitted for testing. We describe here the clinical and laboratory characteristics of the first 50 adult cases with confirmed pandemic (H1N1) 2009. Materials and Methods: A review was conducted of medical notes of adult patients with confirmed pandemic (H1N1) 2009 by polymerase chain reaction assay from combined nasal and throat swabs admitted to the Communicable Disease Centre, Tan Tock Seng Hospital. Results: From 26 May to 18 June 2009, 50 patients with a median age of 27 years old were admitted at a median of 3 days from illness onset. Half were male and all were travellers arriving in Singapore. Non-Singaporean citizens (38%) and other ethnic groups (40%) were over-represented. History of fever was reported in 90% and respiratory symptoms in 92%. Gastrointestinal symptoms were uncommon, present in 4% only. Temperatures on presentation of ≥38.0ºC, ≥37.8ºC and ≥37.5ºC were present in 48%, 56% and 76%, respectively. Only 46% of patients met the United States Centers for Disease Control and Prevention (US CDC) case definition of influenza-like illness (ILI). Clinical and laboratory findings were unremarkable for the majority. All cases were treated with oseltamivir and had uncomplicated recovery. Conclusion: Pandemic (H1N1) 2009 had mild clinical and laboratory findings in immunocompetent patients. Use of the US CDC ILI criteria alone would have detected less than half of confirmed cases.
Key words: Emerging infections, Influenza, Outbreak containment
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Kim HL, Jeon HH, Kim M, Kang CH, Park KH. Laboratory Confirmatory Rate of Pandemic Influenza (H1N1 2009) Virus in Korean Households with Index Case. Infect Chemother 2009. [DOI: 10.3947/ic.2010.42.2.82] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
| | | | - Min Kim
- Armed Forces Seoul Hospital, Seoul, Korea
| | | | - Kyung-Hwa Park
- Department of Infectious Diseases, Chonnam National University Medical School, Gwangju, Korea
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