Surveillance for avian influenza A (H7N9) virus in outer environment and incidence trend of human infection with H7N9 virus in Jiangmen, Guangdong

Objective To understand the distribution of avian influenza A (H7N9) virus in outer environment and the incidence trend of human infection with H7N9 virus in Jiangmen, to provide evidence for the prevention and control H7N9 virus infection. Methods Five poultry wholesale markets and 33 farm produce markets in communities were selected for the study in Jiangmen from January 2014 to February 2015, the environmental samples were collected by using swab smear. Influenza A virus nucleic acid was detected by fluorescence quantitative RT-PCR, and descriptive epidemiological analysis was conducted on the incidence data of human infection with H7N9 virus. Results During the 14 months surveillance, a total of 989 samples were collected, the positive rate of H7N9 virus was 7.48%. Among the 6 kinds of poultry, the highest positive rate was from chicken specimens (8.88%), the difference was significant (2=10.02, P0.05). The positive rate of cutting board and knife smears was higher than that of the smears of inner surfaces and ground surfaces of cage frames, the difference was significant (2=74.39, P0.01). The positive rate was 8.44% (70/829) in winter and spring (December to May) and 2.50%(4/160) in summer and autumn (June to November), the difference was significant (2=6.01, P0.05). Nine cases of human infection with H7N9 virus were reported, the cases mainly occurred sporadically in January and February (88.89%). Conclusion Avian influenza A (H7N9) virus spread in the alive poultry markets in Jiangmen in winter and spring. The incidence of human infection with H7N9 virus had obvious seasonality with the peak in winter and spring.