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. 2016 Aug 30;3(3):ofw182.
doi: 10.1093/ofid/ofw182. eCollection 2016 Sep.

Risk Factors for Influenza A(H7N9) Disease in China, a Matched Case Control Study, October 2014 to April 2015

Lei Zhou  1 , Ruiqi Ren  1 , Jianming Ou  2 , Min Kang  3 , Xiaoxiao Wang  4 , Fiona Havers  5 , Xiang Huo  6 , Xiaoqing Liu  7 , Qianlai Sun  8 , Yongchao He  9 , Bo Liu  1 , Shenggen Wu  2 , Yali Wang  1 , Haitian Sui  1 , Yongjie Zhang  10 , Shaopei Tang  10 , Caiyun Chang  10 , Lunhui Xiang  10 , Dong Wang  1 , Shiguang Zhao  1 , Suizan Zhou  5 , Tao Chen  11 , Nijuan Xiang  1 , Carolyn M Greene  5 , Yanping Zhang  1 , Yuelong Shu  11 , Zijian Feng  12 , Qun Li  1
Affiliations

Risk Factors for Influenza A(H7N9) Disease in China, a Matched Case Control Study, October 2014 to April 2015

Lei Zhou et al. Open Forum Infect Dis. .

Abstract

Background. Human infections with avian influenza A(H7N9) virus have been associated with exposure to poultry and live poultry markets (LPMs). We conducted a case-control study to identify additional and more specific risk factors. Methods. Cases were laboratory-confirmed A(H7N9) infections in persons in China reported from October 1, 2014 to April 30, 2015. Poultry workers, those with insufficient data, and those refusing participation were excluded. We matched up to 4 controls per case by sex, age, and residential community. Using conditional logistic regression, we examined associations between A(H7N9) infection and potential risk factors. Results. Eighty-five cases and 334 controls were enrolled with similar demographic characteristics. Increased risk of A(H7N9) infection was associated with the following: visiting LPMs (adjusted odds ratio [aOR], 6.3; 95% confidence interval [CI], 2.6-15.3), direct contact with live poultry in LPMs (aOR, 4.1; 95% CI, 1.1-15.6), stopping at a live poultry stall when visiting LPMs (aOR, 2.7; 95% CI, 1.1-6.9), raising backyard poultry at home (aOR, 7.7; 95% CI, 2.0-30.5), direct contact with backyard poultry (aOR, 4.9; 95% CI, 1.1-22.1), and having ≥1 chronic disease (aOR, 3.1; 95% CI, 1.5-6.5). Conclusions. Our study identified raising backyard poultry at home as a risk factor for illness with A(H7N9), suggesting the need for enhanced avian influenza surveillance in rural areas.

Keywords: avian influenza A(H7N9); case-control study; risk factor.

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