Epidemiology of Human Infections with Avian Influenza A(H7N9) Virus in China

Qun Li(Apple (Israel)), Lei Zhou, Minghao Zhou(Jiangsu Provincial Center for Disease Control and Prevention), Zhiping Chen(Zhejiang Center for Disease Control and Prevention), Fu‐Rong Li(Anhui Provincial Center for Disease Control and Prevention), Huanyu Wu(Taiwan Centers for Disease Control), Nijuan Xiang, Enfu Chen(Zhejiang Center for Disease Control and Prevention), Fenyang Tang(Jiangsu Provincial Center for Disease Control and Prevention), Dayan Wang(National Institute for Viral Disease Control and Prevention), Ling Meng, Zhiheng Hong, Wenxiao Tu, Yang Cao, Leilei Li, Fan Ding, Bo Liu, Mei Wang, Rongheng Xie, Rongbao Gao(National Institute for Viral Disease Control and Prevention), Xiaodan Li(National Institute for Viral Disease Control and Prevention), Tian Bai(National Institute for Viral Disease Control and Prevention), Shumei Zou(National Institute for Viral Disease Control and Prevention), Jun He, Jiayu Hu(Taiwan Centers for Disease Control), Yangting Xu(Nanjing Municipal Center for Disease Control And Prevention), Chengliang Chai(Zhejiang Center for Disease Control and Prevention), Shiwen Wang(National Institute for Viral Disease Control and Prevention), Yongjun Gao, Lianmei Jin, Yanping Zhang, Huiming Luo(Chinese Center For Disease Control and Prevention), Hongjie Yu(Chinese Center For Disease Control and Prevention), Jianfeng He, Qi Li(Apple (Israel)), Xianjun Wang(Shandong Center for Disease Control and Prevention), Lidong Gao(Hunan Provincial Center for Disease Control and Prevention), Xinghuo Pang(Taiwan Centers for Disease Control), Guo‐Hua Liu(Henan Provincial Center for Disease Control and Prevention), Yan Yan-sheng(Gansu Provincial Center for Disease Control and Prevention), Hui Yuan(Chinese Center For Disease Control and Prevention), Yuelong Shu(National Institute for Viral Disease Control and Prevention), Weizhong Yang(Chinese Center For Disease Control and Prevention), Yu Wang(Chinese Center For Disease Control and Prevention), Fan Wu(Taiwan Centers for Disease Control), Timothy M. Uyeki(Centers for Disease Control and Prevention), Zijian Feng
New England Journal of Medicine
April 24, 2013
10.1056/nejmoa1304617
Cited by 692Open Access
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Abstract

BACKGROUND: The first identified cases of avian influenza A(H7N9) virus infection in humans occurred in China during February and March 2013. We analyzed data obtained from field investigations to describe the epidemiologic characteristics of H7N9 cases in China identified as of December 1, 2013. METHODS: Field investigations were conducted for each confirmed case of H7N9 virus infection. A patient was considered to have a confirmed case if the presence of the H7N9 virus was verified by means of real-time reverse-transcriptase-polymerase-chain-reaction assay (RT-PCR), viral isolation, or serologic testing. Information on demographic characteristics, exposure history, and illness timelines was obtained from patients with confirmed cases. Close contacts were monitored for 7 days for symptoms of illness. Throat swabs were obtained from contacts in whom symptoms developed and were tested for the presence of the H7N9 virus by means of real-time RT-PCR. RESULTS: Among 139 persons with confirmed H7N9 virus infection, the median age was 61 years (range, 2 to 91), 71% were male, and 73% were urban residents. Confirmed cases occurred in 12 areas of China. Nine persons were poultry workers, and of 131 persons with available data, 82% had a history of exposure to live animals, including chickens (82%). A total of 137 persons (99%) were hospitalized, 125 (90%) had pneumonia or respiratory failure, and 65 of 103 with available data (63%) were admitted to an intensive care unit. A total of 47 persons (34%) died in the hospital after a median duration of illness of 21 days, 88 were discharged from the hospital, and 2 remain hospitalized in critical condition; 2 patients were not admitted to a hospital. In four family clusters, human-to-human transmission of H7N9 virus could not be ruled out. Excluding secondary cases in clusters, 2675 close contacts of case patients completed the monitoring period; respiratory symptoms developed in 28 of them (1%); all tested negative for H7N9 virus. CONCLUSIONS: Most persons with confirmed H7N9 virus infection had severe lower respiratory tract illness, were epidemiologically unrelated, and had a history of recent exposure to poultry. However, limited, nonsustained human-to-human H7N9 virus transmission could not be ruled out in four families.

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