title: Detection of avian influenza A(H7N9) virus from live poultry markets in Guangzhou, China: a surveillance report.
abstract: OBJECTIVE
  A virologic surveillance program for A(H7N9) virus was conducted from April 15, 2013 to February 14, 2014 in Guangzhou, aiming to clarify the geographical distribution of A(H7N9) viruses among live poultry markets (LPMs) and poultry farms in Guangzhou. Virological and serological surveys of poultry workers were also conducted to evaluate the risk of poultry-to-human transmission of the A(H7N9) virus.
  
  
  METHODS
  36 retail LPMs, 6 wholesale LPMs and 8 poultry farms were involved in our surveillance program. About 20 live poultry and environmental samples were obtained from each surveillance site at every sampling time. Different environmental samples were collected to represent different poultry-related work activities. RT-PCR and virus culture were performed to identify the A(H7N9) virus. Hemagglutinin inhibition assay and RT-PCR were conducted to detect possible A(H7N9) infection among poultry workers.
  
  
  RESULTS
  A total of 8900 live poultry and environmental samples were collected, of which 131(1.5%) were tested positive for A(H7N9) virus. 44.4% (16/36) of retail LPMs and 50.0% (3/6) of wholesale LPMs were confirmed to be contaminated. No positive samples was detected from poultry farms. A significant higher positive sample rate was found in environmental samples related to poultry selling (2.6%) and slaughtering (2.4%), compared to poultry holding (0.9%). Correspondingly, A(H7N9) viruses were isolated most frequently from slaughter zone. In addition, 316 poultry workers associated with the 19 contaminated-LPMs were recruited and a low seroprevalence (1.6%) of antibody against A(H7N9) virus was detected. An asymptomatic A(H7N9) infection was also identified by RT-PCR.
  
  
  CONCLUSIONS
  Our study highlights the importance of conducting effective surveillance for A(H7N9) virus and provides evidence to support the assumption that slaughtering is the key process for the propagation of A(H7N9) virus in retail LPMs. Moreover, the ability of A(H7N9) virus to cross species barrier is proved to be still limited.
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou, Guangdong, China.
authors.forename: Zongqiu
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou, Guangdong, China.
authors.forename: Kuibiao
authors.initials: K
authors.lastname: Li
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou, Guangdong, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Luo
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou, Guangdong, China.
authors.forename: Enjie
authors.initials: E
authors.lastname: Lu
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou, Guangdong, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yuan
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou, Guangdong, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou, Guangdong, China.
authors.forename: Jianyun
authors.initials: J
authors.lastname: Lu
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou, Guangdong, China.
authors.forename: Biao
authors.initials: B
authors.lastname: Di
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou, Guangdong, China.
authors.forename: Xincai
authors.initials: X
authors.lastname: Xiao
authors.affiliation: Guangzhou Center for Disease Control and Prevention, Guangzhou, Guangdong, China.
authors.forename: Zhicong
authors.initials: Z
authors.lastname: Yang
mesh_terms: D000818:Animals; D002681:China / Q000453:epidemiology; D006801:Humans; D064766:Influenza A Virus, H7N9 Subtype / Q000235:genetics / Q000302:isolation & purification*; D005585:Influenza in Birds / Q000453:epidemiology / Q000473:pathology / Q000821:virology*; D007251:Influenza, Human / Q000453:epidemiology; D011200:Poultry / Q000821:virology*; D016036:Seroepidemiologic Studies