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Open Access Highly Accessed Research article

Epidemiologic characterization of 30 confirmed cases of human infection with avian influenza A(H7N9) virus in Hangzhou, China

Hua Ding1, Li Xie1, Zhou Sun1, Qing-Jun Kao1, Ren-Jie Huang1, Xu-Hui Yang1, Chun-ping Huang1, Yuan-Yuan Wen1*, Jing-Cao Pan1, Xiao-Ying Pu1, Tao Jin2, Xiao-Hong Zhou3, Lin Zheng4, Jian Li5 and Feng-Juan Wang6

Author Affiliations

1 Hangzhou Center for Disease Control and Prevention, Hangzhou 310021, China

2 Shangcheng District Center for Disease Control and Prevention, Hangzhou 310009, China

3 Xiacheng District Center for Disease Control and Prevention, Hangzhou 310003, China

4 Xihu District Center for Disease Control and Prevention, Hangzhou 300013, China

5 Jianggan District Center for Disease Control and Prevention, Hangzhou 310004, China

6 Xiaoshan District Center for Disease Control and Prevention, Hangzhou 311201, China

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BMC Infectious Diseases 2014, 14:175  doi:10.1186/1471-2334-14-175

Published: 31 March 2014

Abstract

Background

We examined the clinical and epidemiological characteristics of 30 cases of human infection with avian influenza A(H7N9) virus in Hangzhou and investigated their external environments to provide evidence for contact tracing and disease prevention and control.

Methods

The cases confirmed from April 1 through May 1, 2013 were studied. Field epidemiologic surveys were conducted to collect the clinical and epidemiologic data. Case-related and environmental specimens were collected for etiologic detection.

Results

Thirty cases of human infection with avian influenza A(H7N9) virus were confirmed in Hangzhou from April 1 through May 1, 2013, including one pregnant woman and three deaths. The median age of the patients was 62 years (range: 38–86 years). Twenty-three of the patients were men (76.67%). The median duration between disease onset and occurrence of respiratory failure and confirmed diagnosis was 5 and 6 days, respectively. Maximum medical observation of 666 close contacts of the patients revealed no irregularity. Of 314 external environmental specimens, the overall positive detection rate of H7N9 nucleic acid was 28.98%. Eight districts of Hangzhou city had positive detections in the external environments, the highest rate being in Yuhang District (78.13%). Statistical analysis of the specimen collection locations indicates a significant difference between the case-linked locations and the non-case locations (χ2 = 16.563, p < 0.05) in terms of H7N9 viral nucleic acid detection rate. No epidemiologic link has been found among the 30 cases.

Conclusions

Most of the infected were retired individuals aged 60 years or older. Men made the majority. The cases are sporadic at present, with no evidence of human-to-human transmission. Exposures to poultry and live poultry markets may be important sources of infection.

Keywords:
Human avian influenza; H7N9 subtype; Epidemiologic characteristics; External environmental detection