Environmental avian influenza surveillance and current status of human infection with avian influenza A(H7N9)virus in Jiuquan, Gansu, 2014-2017

Objective To analyze the surveillance results of avian influenza in poultry related environment in Jiuquan of Gansu province and provide evidence for the early warning and prevention of human infection with avian influenza A (H7N9) virus. Methods Different environmental samples were collected from live poultry markets in different counties (district)of Jiuquan from 2014 to 2017 for the nucleic acid detection of avian influenza viruses by using real-time PCR, and the results were used for statistical analysis. Results A total of 1 091 environmental samples were collected,in which 231 samples were positive foe avian influenza virus nucleic acid (21.17%),including 162 A (H9N2)positive samples (70.13%),51 A (H7N9) positive samples (22.08%)and 18 samples which were positive for both A (H7)and A (H9)viruses (7.79%). From 2014 to 2016,only avian influenza A (H9N2)virus was detected,the annual positive rate of influenza virus nucleic acid were 3.23%, 22.05% and 31.32% respectively. In 2017,the positive rate of influenza virus nucleic acid was 19.31%,the positive rate was 52.41% for A (H9N2)virus (76 strains), 35.17% for A (H7N9)virus (51 strains)and 12.41% for both A (H7)and A (H9) viruses (18 strains). The detection rate of influenza virus was highest in urban and rural live poultry markets (30.14%), followed by that in poultry farms (11.79%)of and in poultry slaughtering and processing sites (10.23%). Among the different types of samples,the detection rate in sewage samples was highest,followed by that in chopping board samples and in poultry drinking water samples. There were significant differences in positive rate among different years,different surveillance sites and different types of samples. The first human case of avian influenza A (H7N9)virus infection in Gansu province was detected by active surveillance after A (H7N9)virus nucleic acid was detected in poultry. Conclusion Environmental surveillance results of influenza virus is the important evidence for the early warning of human infection with avian influenza A (H7N9)virus. It is important to strengthen the surveillance.