Influenza A Virus Shedding and Infectivity in Households
Open Access
- 15 April 2015
- journal article
- research article
- Published by Oxford University Press (OUP) in The Journal of Infectious Diseases
- Vol. 212 (9), 1420-1428
- https://doi.org/10.1093/infdis/jiv225
Abstract
Background. Viral shedding is often considered to correlate with the infectivity of influenza, but the evidence for this is limited. Methods. In a detailed study of influenza virus transmission within households in 2008–2012, index case patients with confirmed influenza were identified in outpatient clinics, and we collected nose and throat swab specimens for testing by reverse-transcription polymerase chain reaction from all household members regardless of illness. We used individual-based hazard models to characterize the relationship between viral load (V) and infectivity. Results. Assuming that infectivity was proportional to viral load V gave the worst fit, because it strongly overestimated the proportion of transmission occurring at symptom onset. Alternative models assuming that infectivity was proportional to a various functions of V provided better fits, although they all overestimated the proportion of transmission occurring >3 days after symptom onset. The best fitting model assumed that infectivity was proportion to Vγ, with estimates of γ = 0.136 and γ = 0.156 for seasonal influenza A(H1N1) and A(H3N2) respectively. Conclusions. All the models we considered that used viral loads to approximate infectivity of a case imperfectly explained the timing of influenza secondary infections in households. Identification of more accurate correlates of infectivity will be important to inform control policies and disease modeling.Keywords
Funding Information
- National Institute of Allergy and Infectious Diseases (NIAID) (HHSN266200700005C)
- NIAID Centers for Excellence in Influenza Research and Surveillance (N01-AI-70005)
- The Government of the Hong Kong Special Administrative Region (HK-10-04-02)
- the Health and Medical Research Fund
- National Institute of General Medical Sciences (U54 GM088558)
- the Harvard Center for Communicable Disease Dynamics and MIDAS initiative (1U01GM110721-01 to S. C.)
- The Area of Excellence Scheme of the University Grants Committee of Hong Kong (AoE/M-12/06)
- L'Oreal Hong Kong (research scholarship to T. K. T)
- the Laboratory of Excellence Integrative Biology of Emerging Infectious Diseases (research funding to S. C.)
This publication has 41 references indexed in Scilit:
- The Epidemiology of Interpandemic and Pandemic Influenza in Vietnam, 2007–2010American Journal of Epidemiology, 2012
- Validation of Self-swab for Virologic Confirmation of Influenza Virus Infections in a Community SettingThe Journal of Infectious Diseases, 2011
- Viral genetic sequence variations in pandemic H1N1/2009 and seasonal H3N2 influenza viruses within an individual, a household and a communityJournal of Clinical Virology, 2011
- Role of social networks in shaping disease transmission during a community outbreak of 2009 H1N1 pandemic influenzaProceedings of the National Academy of Sciences, 2011
- Viral Shedding and Clinical Illness in Naturally Acquired Influenza Virus InfectionsThe Journal of Infectious Diseases, 2010
- Effects of Oseltamivir Treatment on Duration of Clinical Illness and Viral Shedding and Household Transmission of Influenza VirusClinical Infectious Diseases, 2010
- Comparison of nasopharyngeal flocked swabs and aspirates for rapid diagnosis of respiratory viruses in childrenJournal of Clinical Virology, 2008
- Time Lines of Infection and Disease in Human Influenza: A Review of Volunteer Challenge StudiesAmerican Journal of Epidemiology, 2008
- Strategies for mitigating an influenza pandemicNature, 2006
- A Bayesian MCMC approach to study transmission of influenza: application to household longitudinal dataStatistics in Medicine, 2004