title: Retrospective study of risk factors for mortality in human avian influenza A(H7N9) cases in Zhejiang Province, China, March 2013 to June 2014.
abstract: BACKGROUND
  The influenza A(H7N9) virus causes a serious disease that threatens human health. Fatalities associated with human infections caused by this virus are of great public health concern; however, the possible risk factors are not yet fully known.
  
  
  METHODS
  A stratified sampling method, incorporating household income levels and a random number table method, was used to select laboratory-confirmed A(H7N9) cases for this study. Eighty-five patients were selected randomly from 139 laboratory-confirmed A(H7N9) cases occurring in Zhejiang Province between March 1, 2013 and June 30, 2014. Data were collected using a standard method. To test the statistical significance among discrete variables, univariate analyses were used to compare two groups. The Kaplan-Meier product-limit method was used to analyze the patient survival fraction. The Cox proportional hazards regression model was used to analyze all variables with p ≤ 0.05 in the univariate analysis. Lastly, a stepwise procedure was used to construct a final model with a significance level of p > 0.10 for removal and p<0.05 for re-entry.
  
  
  RESULTS
  A total of 85 patients with H7N9 virus infection were identified. Among these, 30 (35.29%) died. In the univariate analysis, the following factors were associated with a high risk of influenza A(H7N9) case fatality: age ≥ 60 years (p=0.008), low education level (p=0.030), chronic diseases (p=0.029), poor hand hygiene (p=0.010), time from illness onset to the first medical visit (p=0.029) and to intensive care unit admission (p=0.008), an incubation period of ≤ 5 days (p=0.039), a peak C-reactive protein ≥ 120 mg/l (p=0.012), increased initial neutrophil count (p=0.020), decreased initial lymphocyte count (p=0.021), and initial infection of both lungs (p=0.003). Multivariate analysis confirmed that the independent predictors of H7N9 virus infection mortality in Zhejiang, China were hand hygiene (hazard ratio (HR) 5.163, 95% confidence interval (CI) 1.164-22.661), age (HR 1.042, 95% CI 1.007-1.076), and peak CRP (HR 1.009, 95% CI 1.002-1.016).
  
  
  CONCLUSIONS
  Improvements in immunity, early case identification and treatment, and personal protection measures are key to addressing the high human avian influenza A(H7N9) case fatality rate.
authors.affiliation: Division of Infectious Diseases, Hangzhou Center for Disease Control and Prevention, 1 Mingshi Road, Hangzhou 310021, China; Department of Adolescents and Children Health, School of Public Health, Medical College of Soochow University, Suzhou 215123, China.
authors.forename: Qing-Lin
authors.initials: QL
authors.lastname: Cheng
authors.affiliation: Division of Infectious Diseases, Hangzhou Center for Disease Control and Prevention, 1 Mingshi Road, Hangzhou 310021, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Ding
authors.affiliation: Division of Infectious Diseases, Hangzhou Center for Disease Control and Prevention, 1 Mingshi Road, Hangzhou 310021, China.
authors.forename: Zhou
authors.initials: Z
authors.lastname: Sun
authors.affiliation: Division of Infectious Diseases, Hangzhou Center for Disease Control and Prevention, 1 Mingshi Road, Hangzhou 310021, China.
authors.forename: Qing-Jun
authors.initials: QJ
authors.lastname: Kao
authors.affiliation: Division of Infectious Diseases, Hangzhou Center for Disease Control and Prevention, 1 Mingshi Road, Hangzhou 310021, China.
authors.forename: Xu-Hui
authors.initials: XH
authors.lastname: Yang
authors.affiliation: Division of Infectious Diseases, Hangzhou Center for Disease Control and Prevention, 1 Mingshi Road, Hangzhou 310021, China.
authors.forename: Ren-Jie
authors.initials: RJ
authors.lastname: Huang
authors.affiliation: Division of Infectious Diseases, Hangzhou Center for Disease Control and Prevention, 1 Mingshi Road, Hangzhou 310021, China.
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Wen
authors.affiliation: Division of Infectious Diseases, Hangzhou Center for Disease Control and Prevention, 1 Mingshi Road, Hangzhou 310021, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: Division of Infectious Diseases, Hangzhou Center for Disease Control and Prevention, 1 Mingshi Road, Hangzhou 310021, China. Electronic address: hbxieli@yeah.net.
authors.forename: Li
authors.initials: L
authors.lastname: Xie
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D002681:China / Q000453:epidemiology; D005260:Female; D063373:Hand Hygiene; D006801:Humans; D064766:Influenza A Virus, H7N9 Subtype; D007251:Influenza, Human / Q000401:mortality*; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors
keywords: H7N9 subtype; Influenza; Influenza A virus; Outcome; Risk factors; human