Xiling Wang1, Peng Wu2, Yao Pei1, Tim K Tsang3, Dantong Gu1, Wei Wang1, Juanjuan Zhang1, Peter W Horby4, Timothy M Uyeki5, Benjamin J Cowling2, Hongjie Yu1. 1. School of Public Health, Fudan University, Key Laboratory of Public Health Safety, Ministry of Education, Shanghai. 2. World Health Organization Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China. 3. Department of Biostatistics, College of Public Health and Health Professions & College of Medicine, University of Florida, Gainesville. 4. Center for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, United Kingdom. 5. Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
Abstract
Background: The 2016-17 epidemic of human infections with avian influenza A(H7N9) virus was alarming, due to the surge in reported cases across a wide geographic area and the emergence of highly-pathogenic A(H7N9) viruses. Our study aimed to assess whether the human-to-human transmission risk of A(H7N9) virus has changed across the 5 waves since 2013. Methods: Data on human cases and clusters of A(H7N9) virus infection were collected from the World Health Organization, open access national and provincial reports, informal online sources, and published literature. We compared the epidemiological characteristics of sporadic and cluster cases, estimated the relative risk (RR) of infection in blood relatives and non-blood relatives, and estimated the bounds on the effective reproductive number (Re) across waves from 2013 through September 2017. Results: We identified 40 human clusters of A(H7N9) virus infection, with a median cluster size of 2 (range 2-3). The overall RR of infection in blood relatives versus non-blood relatives was 1.65 (95% confidence interval [CI]: 0.88, 3.09), and was not significantly different across waves (χ2 = 2.66, P = .617). The upper limit of Re for A(H7N9) virus was 0.12 (95% CI: 0.10, 0.14) and was not significantly different across waves (χ2 = 1.52, P = .822). Conclusions: The small cluster size and low Re suggest that human-to-human transmissibility of A(H7N9) virus has not changed over time and remains limited to date. Continuous assessment of A(H7N9) virus infections and human case clusters is of crucial importance for public health.
Background: The 2016-17 epidemic of humaninfections with avian influenza A(H7N9) virus was alarming, due to the surge in reported cases across a wide geographic area and the emergence of highly-pathogenic A(H7N9) viruses. Our study aimed to assess whether the human-to-human transmission risk of A(H7N9) virus has changed across the 5 waves since 2013. Methods: Data on human cases and clusters of A(H7N9) virus infection were collected from the World Health Organization, open access national and provincial reports, informal online sources, and published literature. We compared the epidemiological characteristics of sporadic and cluster cases, estimated the relative risk (RR) of infection in blood relatives and non-blood relatives, and estimated the bounds on the effective reproductive number (Re) across waves from 2013 through September 2017. Results: We identified 40 humanclusters of A(H7N9) virus infection, with a median cluster size of 2 (range 2-3). The overall RR of infection in blood relatives versus non-blood relatives was 1.65 (95% confidence interval [CI]: 0.88, 3.09), and was not significantly different across waves (χ2 = 2.66, P = .617). The upper limit of Re for A(H7N9) virus was 0.12 (95% CI: 0.10, 0.14) and was not significantly different across waves (χ2 = 1.52, P = .822). Conclusions: The small cluster size and low Re suggest that human-to-human transmissibility of A(H7N9) virus has not changed over time and remains limited to date. Continuous assessment of A(H7N9) virus infections and human case clusters is of crucial importance for public health.
Authors: Ying Qin; Peter W Horby; Tim K Tsang; Enfu Chen; Lidong Gao; Jianming Ou; Tran Hien Nguyen; Tran Nhu Duong; Viktor Gasimov; Luzhao Feng; Peng Wu; Hui Jiang; Xiang Ren; Zhibin Peng; Sa Li; Ming Li; Jiandong Zheng; Shelan Liu; Shixiong Hu; Rongtao Hong; Jeremy J Farrar; Gabriel M Leung; George F Gao; Benjamin J Cowling; Hongjie Yu Journal: Clin Infect Dis Date: 2015-05-04 Impact factor: 9.079
Authors: Victor Virlogeux; Ming Li; Tim K Tsang; Luzhao Feng; Vicky J Fang; Hui Jiang; Peng Wu; Jiandong Zheng; Eric H Y Lau; Yu Cao; Ying Qin; Qiaohong Liao; Hongjie Yu; Benjamin J Cowling Journal: Am J Epidemiol Date: 2015-09-26 Impact factor: 4.897
Authors: Dennis K M Ip; Qiaohong Liao; Peng Wu; Zhancheng Gao; Bin Cao; Luzhao Feng; Xiaoling Xu; Hui Jiang; Ming Li; Jing Bao; Jiandong Zheng; Qian Zhang; Zhaorui Chang; Yu Li; Jianxing Yu; Fengfeng Liu; Michael Y Ni; Joseph T Wu; Benjamin J Cowling; Weizhong Yang; Gabriel M Leung; Hongjie Yu Journal: BMJ Date: 2013-06-24
Authors: Min Kang; Eric H Y Lau; Wenda Guan; Yuwei Yang; Tie Song; Benjamin J Cowling; Jie Wu; Malik Peiris; Jianfeng He; Chris Ka Pun Mok Journal: Euro Surveill Date: 2017-07-06
Authors: James C Kile; Ruiqi Ren; Liqi Liu; Carolyn M Greene; Katherine Roguski; A Danielle Iuliano; Yunho Jang; Joyce Jones; Sharmi Thor; Ying Song; Suizan Zhou; Susan C Trock; Vivien Dugan; David E Wentworth; Min Z Levine; Timothy M Uyeki; Jacqueline M Katz; Daniel B Jernigan; Sonja J Olsen; Alicia M Fry; Eduardo Azziz-Baumgartner; C Todd Davis Journal: MMWR Morb Mortal Wkly Rep Date: 2017-09-08 Impact factor: 17.586