Surveillance for avian influenza A (H7N9) virus in external environment from 2015 to 2017 in Taizhou, Zhejiang

Objective To understand the surveillance results of avian influenza A (H7N9) virus in exter-nal environment in Taizhou city of Zhejiang province form 2015 to 2017, so as to explore prevention and control strategies in Taizhou. Methods The samples were collected from live poultry related environments from 2015 to 2017 for detection of H7 and N9 subtype by RT-PCR, and the results were statistically analyzed. Results A total of 466 poultry related sites were surveyed, and the positive rate of H7N9 strains was 13.95% (65 sites) . A total of 2 848 samples were collected, and the positive rate of H7N9 strains was 4.46% which were consistent with the distribution of the case onset (r=0.93, P<0.05) with the peak periods from January to February and from May to June each year. Among different samples, the washing sewage (31 samples, 9.78%) , areas of Linhai city (47 samples, 12.53%) , Xianju county (22 samples, 6.38%) and Sanmen county (20 samples, 6.29%) had the high positive rates. The positive sites were mainly in urban and rural live poultry markets (20.19%) and poultry packinghouses (25.00%) , while the rest sites were negative. The positive site rates were highest in Linhai city (30.99%) , followed by Wenling city (23.08%) and Xianju county (17.54%) . The differences of sample types, site types and areas (sample and site) in positive rates were significant (χ2=40.931, 34.197, 105.292 and 39.632, P<0.05) . Conclusions The circulation of H7N9 virus is still serious in Taizhou. Winter, spring and May to June are peak periods of circulation, while the live poultry markets and poultry slaughter plants are the main virus transmission sites. Therefore, surveillance and disinfection management should be emphasized. Key words: Influenza in birds; H7N9; Surveillance