Transmission Potential of Influenza A(H7N9) Virus, China, 2013–2014 - Volume 21, Number 5—May 2015 - Emerging Infectious Disease journal - CDC

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Transmission Potential of Influenza A(H7N9) Virus, China, 2013–2014 - Volume 21, Number 5—May 2015 - Emerging Infectious Disease journal - CDC

Volume 21, Number 5—May 2015

Dispatch

Transmission Potential of Influenza A(H7N9) Virus, China, 2013–2014

On This Page

• The Study
• Conclusions
• Suggested Citation

Figures

• Figure 1
• Figure 2

Tables

• Table

Technical Appendicies

• Technical Appendix

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Adam J. Kucharski1 , Harriet L. Mills1, Christl A. Donnelly, and Steven Riley

Author affiliations: London School of Hygiene and Tropical Medicine, London, UK (A.J. Kucharski); National Institutes of Health, Bethesda, Maryland, USA (A.J. Kucharski); Imperial College London, London (A.J. Kucharski, H.L. Mills, C.A. Donnelly, S. Riley)

Suggested citation for this article

Abstract

To determine transmission potential of influenza A(H7N9) virus, we used symptom onset data to compare 2 waves of infection in China during 2013–2014. We found evidence of increased transmission potential in the second wave and showed that live bird market closure was significantly less effective in Guangdong than in other regions.

From February 19, 2013, through April 22, 2014, a total of 429 cases of influenza A(H7N9) virus infection in humans in China were reported and occurred in 2 outbreak waves. During the first wave in spring 2013, live bird markets were closed in several parts of China (1,2); these market closures substantially reduced the risk for infection in affected regions (3). During a second wave in autumn 2013 (4), markets were again closed in some provinces (5–7). Analysis of the largest clusters of subtype H7N9 virus infection in 2013 suggested that the basic reproduction number (R0, the average number of secondary cases generated by a typical infectious host in a fully susceptible population) was higher in some clusters than in others (8,9), although the absence of sustained transmission implied that R0 was less than the critical value of 1. To determine the transmission potential of influenza A(H7N9) virus in the first and second waves in 2013, we compared symptom onset data. We also measured the extent to which market closures in 2014 reduced spillover hazard (i.e., risk for animal-to-human infection).

Dr. Kucharski is a research fellow in infectious disease epidemiology at the London School of Hygiene and Tropical Medicine. His research focuses on the dynamics of emerging infections and how population structure and social behavior shape disease transmission at the animal–human interface. Dr. Mills is a postdoctoral research associate in the Medical Research Council Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London. Her research includes examination of human mobility patterns and their influence on disease transmission and the analysis of emerging epidemics.

Acknowledgment

This work was funded by the Wellcome Trust (project grant 093488/Z/10/Z); the Medical Research Council (United Kingdom, project grant MR/J008761/1; Fellowship MR/K021524/1); National Institute for General Medical Sciences (United States, MIDAS U01 GM110721-01); the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 278433-PREDEMICS; the Fogarty International Center (United States, R01 TW008246-01); and the Research and Policy for Infectious Disease Dynamics program also from Fogarty International Center with the Science and Technology Directorate, Department of Homeland Security.

References

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Figures

• Figure 1. Spatial and temporal distribution of reported cases of influenza A(H7N9) virus infection among humans, China, 2013–2014. Onset of the first case in wave 1 was February 19, 2013 (although...
• Figure 2. A posteriori probability estimates of spillover hazard for influenza A(H7N9) virus infection in China, by region. Black dots show total number of reported influenza A(H7N9) virus cases for which...

Table

• Table. Estimates of human-to-human transmission and effectiveness of live bird market closures, China, 2013–2014

Technical Appendix

• Technical Appendix. Additional data for influenza A(H7N9) virus transmission model and effectiveness of live bird market closure, China, 2013­—2014.  546 KB

Suggested citation for this article: Kucharski AJ, Mills HL, Donnelly CA, Riley S. Transmission potential of influenza A(H7N9) virus, China, 2013–2014. Emerg Infect Dis. 2015 May [date cited]. http://dx.doi.org/10.3201/eid2105.141137

DOI: 10.3201/eid2105.141137

1These authors contributed equally to this article.