Abstract
PurposeA 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.Methods36 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.ResultsA 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.ConclusionsOur 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.
Highlights
A novel reassortant avian influenza A(H7N9) virus, characterized by rapidly progressive pneumonia, development of acute respiratory distress syndrome and fatal outcomes [1], has emerged in China since February 2013 [2]
After two confirmed A(H7N9) cases were reported in Guangdong province [18,19] and A(H7N9) viruses were detected from several live poultry markets (LPMs) in other cities of Guangdong, the number of retail LPMs selected as surveillance sites was subsequently expanded to 36 on December 1, 2013
LPM practices and poultry source All LPMs involved in this virologic surveillance program operated daily to sell chickens, ducks, geese and pigeons
Summary
A novel reassortant avian influenza A(H7N9) virus, characterized by rapidly progressive pneumonia, development of acute respiratory distress syndrome and fatal outcomes [1], has emerged in China since February 2013 [2]. After a period of quiescence from June to September 2013, during which only 2 laboratory-confirmed cases were reported, a second-wave outbreak of A(H7N9) has re-emerged in Pearl River Delta of south China since November 2013. South China has been considered to be an important origin or even the epicenter of influenza [5], as several avian influenza virus (AIV) subtypes crossing species barrier to infect human were firstly reported in this region [6,7]. The large amount of live poultry processed in LPMs daily, the high population density, and the cultural preference of purchasing freshly slaughtered poultry among households there make it an ideal environment for AIVs to be introduced, to transmit among different avian species, and even to infect humans. AIV human infections have been occasionally reported in Guangzhou [9,10,11,12,13]
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