| Background:Aquatic birds are the nature hosts of all HA(1-16) and NA(1-9) subtypes of influenza viruses. Eventhough only H1and H3subtype viruses are circulating in human, a number of avian influenza viruses can occasionally infect human, such as H9N2, H5N1, H7N2, H7N3, H7N7, etc. In the last two years, human infection of H7N9, H10N8, H6N1and H5N6avian influenza viruses were reported in China. The specific backyard mixed culture mode and live poultry consumption pattern in China increase the risk of produce novel reassortant viruses, which may induce an influenza pandemic. Therefore, strengthen avian influenza surveillance and risk assessment in China is essential for pandemic preparation and control. Since2009, in order to understand the circumstances of human infection of avian influenza H5N1viruses in China, a serology surveillance system based on occupational exposure populations in China has been set up. This study, which is using sera samples collected from this surveillance system, systematically studied seroprevalence of three mainsure avian influenza viruses in humans, including H9N2, H6N2and H6N6.Method:A systimatic and comprehensive seroprevalence study of H9N2and H6influenza viruses were performed using15,700sera samples collected from live poultry market, poultry farm, backyard poultry farm, slaughter factory and nature reserve between2009and2011. A total of5antigenically different antigens were selected for this study, including3H9N2viruses (A/Guangzhou/333/99-, A/Chicken/AK4/Anhui/2011、A/quail/Hong Kong/G1/97),1H6N2virus (A/Chicken/Y94/Guangdong/2011) and1H6N6virus (A/environment/Hunan/2/2010). Hemagglutination Inhibition (HI) assay was used as primary assay and the result of Microneutralization (MN) assay is considered as the endpoint.Results:The seroprevalence of avian influenza H9N2and H6are3.89%and0.4%, respectivelly.From the point of view of the seroprevalence of different antigens, the seroprevalence of A/Guangzhou/333/99, one of the G9lineage virus isolated quite early, is significantly higher than A/Chicken/AK4/Anhui/2011, which is also belong to G9lineage, and A/quail/Hong Kong/G1/97, which is belong to G1lineage (p<0.0001). The seroprevalence of H6N2virus in occupational exposure populations is significantly higher than H6N6virus (p<0.0001).Regarding to occupational exposure populations, positive sera samples were detected in all populations, but the seroprevalences are significantly different (p<0.05). The seroprevalence of H9N2in live poultry market, poultry workers and backyard exposure populations is significantly higher than butcher and nature reserve workers. The seroprevalence of H6N2virus in occupational exposure populations are significantly different, seroprevalence in live poultry market, backyard poultry farm and nature reserve exposure populations is higher than other exposure populations.In terms of the seroprevalence in different age groups, we found that the seroprevalence of A/Guangzhou/333/99and A/Chicken/AK4/Anhui/2011is increased with the increase of age. The seroprevalence of A/Chicken/AK4/Anhui/2011(H9N2) and H6viruses in different age groups has no significant difference (p>0.05).From geographical point of view, positive samples of H9N2viruses are detected in all22sample collecting provinces except Heilongjiang (n=280). The seroprevalence in South of China is significantly higher than North (p=0.002). Positive sera of H6N2virus are detected in all sample collecting provinces except Henan, Jilin and Liaoning.ConclusionThis is the first time to report human infection of H6avian influenza virus. From the seroprevalence point of view, the risk of occupational exposure populations infection of three major avian influenza viruses circulating in poultry is H9N2, H6and H5N1in order. The result of this study pointed out that the surveillance of avian influenza H9N2and H6viruses in exposure populations in China should be strengthened to efficiently prevent and control the risk of avian influenza virus or novel reassortant virus to human beings. |
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