Characterization of avian influenza A (H4N2) viruses isolated from wild birds in Shanghai during 2019 to 2021

作者：Xu, Yuting; Tang, Ling; Gu, Xiaojun; Bo, Shunqi; Ming, Le; Ma, Min; Zhao, Chenyao; Sun, Kaibo; Liu, Yuyi; He, Guimei^*

来源：Poultry Science, 2023, 102(10): 102948.

DOI：10.1016/j.psj.2023.102948

• H4N2 avian influenza virus
• epidemiology
• phylogenetic analysis
• recombination
• Shanghai

The H4 subtype of avian influenza viruses has been widely distributed among wild birds. During the surveillance of the avian influenza virus in Shanghai from 2019 to 2021, a total of 4,451 samples were collected from wild birds, among which 46 H4 sub-types of avian influenza viruses were identified, account-ing for 7.40% of the total positive samples. The H4 subtype viruses have a wide range of hosts, including the spot-billed duck, common teal, and other wild birds in Anseriformes. Among all H4 subtypes, the most abun-dant are the H4N2 viruses. To clarify the genetic charac-teristics of H4N2 viruses, the whole genome sequences of 20 H4N2 viruses were analyzed. Phylogenetical analysis showed that all 8 genes of these viruses belonged to the Eurasian lineage and closely clustered with low patho-genic avian influenza viruses from countries along the East Asia-Australia migratory route. However, the PB1 gene of 1 H4N2 virus (NH21920) might provide its inter-nal gene for highly pathogenic avian influenza H5N8 viruses in Korea and Japan. At least 10 genotypes were identified in these viruses, indicating that they under-went multiple complex recombination events. Our study has provided a better epidemiological understanding of the H4N2 viruses in wild birds. Considering the muta-tional potential, comprehensive surveillance of the H4N2 virus in both poultry and wild birds is imperative.