Abstract:Wild birds are a natural reservoir for avian influenza virus. The virus can spread to other wild birds and domestic birds during migration. Bohai Bay is an important stopover site located in the East Asian-Australasian Flyway. Every year, a large number of waterbirds rest in Bohai Bay, which accelerated the spread of the virus. To understand the correlation between the transmission and evolution of avian influenza virus and waterbirds migration in Bohai Bay during the spring, 2 120 fecal samples of waders were collected in western Bohai Bay from April to May in 2018. The samples were treated and tested, two strains of H2 subtype avian influenza virus were isolated, and their molecular characteristics and genetic evolution were analyzed. Combining the banding and recovery data of waterbirds, the association between the spread of H2 subtype virus and waterbirds migration was explored. The results showed that the HA protein cleavage site of the two isolates were consistent with the molecular characteristics of low pathogenicity avian influenza virus. All 8 gene fragments of these two strains were not highly homologous. The 8 gene fragments of A/waders/Hebei/879/2018 (H2N7) had the highest homology and the closest genetic relationship with the strains in Fujian and Australia (Table1 for homology and Appendix 1 for genetic relationship). The 8 gene fragments of A/waders/Hebei/854/2018 (H2N8) had the highest homology and the closest genetic relationship with the strains in Hunan, Japan, Korea, Bangladesh and Vietnam, respectively (Table 1 for homology and Appendix 2 for genetic relationship). Based on the banding and recovery data of waterbirds in Bohai bay, AIV 879-H2N7 was spread with the wild bird migration between Bohai Bay, Fujian and Australia, AIV 854-H2N8 was spread and genetic reassortment was taken place with wild bird migration between East Asian-Australasian Flyway and Central Asia-India Flyway.