title: Epidemiologic characterization of 30 confirmed cases of human infection with avian influenza A(H7N9) virus in Hangzhou, China.
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.
authors.forename: Hua
authors.initials: H
authors.lastname: Ding
authors.forename: Li
authors.initials: L
authors.lastname: Xie
authors.forename: Zhou
authors.initials: Z
authors.lastname: Sun
authors.forename: Qing-Jun
authors.initials: QJ
authors.lastname: Kao
authors.forename: Ren-Jie
authors.initials: RJ
authors.lastname: Huang
authors.forename: Xu-Hui
authors.initials: XH
authors.lastname: Yang
authors.forename: Chun-ping
authors.initials: CP
authors.lastname: Huang
authors.affiliation: Hangzhou Center for Disease Control and Prevention, Hangzhou 310021, China. wenyuanyuan1022@126.com.
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Wen
authors.forename: Jing-Cao
authors.initials: JC
authors.lastname: Pan
authors.forename: Xiao-Ying
authors.initials: XY
authors.lastname: Pu
authors.forename: Tao
authors.initials: T
authors.lastname: Jin
authors.forename: Xiao-Hong
authors.initials: XH
authors.lastname: Zhou
authors.forename: Lin
authors.initials: L
authors.lastname: Zheng
authors.forename: Jian
authors.initials: J
authors.lastname: Li
authors.forename: Feng-Juan
authors.initials: FJ
authors.lastname: Wang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002681:China / Q000453:epidemiology; D004783:Environmental Microbiology; D005260:Female; D006801:Humans; D064766:Influenza A Virus, H7N9 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology / Q000821:virology