Etiological surveillance for avian influenza in external environment in Shenzhen during 2015-2019

Objective To analyze the distribution and epidemiological features of avian influenza virus in external environments in Shenzhen during 2015-2019. Methods The external environment samples collected in Shenzhen during 2015-2019 were used to detect nucleic acids of avian influenza virus by real-time fluorescent PCR. The H5, H7 and H9 subtypes were analyzed for positive samples. A database was constructed and the data were analyzed by statistical methods. Results For 4 674 samples collected from December, 2015 to May, 2019, 2 243 samples were positive for FluA with a positive rate of 48.0%. For H5, H7 and H9 subtypes, the numbers of positive samples were 673, 283 and 799, respectively and the positive rates were 14.4%, 6.1% and 17.1%, respectively. In addition, 367 samples were positve for both H5 and H9 subtypes and the positive rate was 7.9%. There were 121 FluA positive samples with no result of subtyping, accounting for about 2.6%. Conclusions The H5 and H9 avian influenza viruses were currently dominant pollutants in external environment. Coexistence of H5 and H9 avian influenza viruses may facilitate viral gene reassortment. Continuous environmental surveillance should be strengthened. Key words: Avian influenza virus; External environment; Nucleic acid detection