Isolation and Identification of Novel Highly Pathogenic Avian Influenza Virus (H5N8) Subclade 2.3.4.4b from Geese in Northeastern China.

H5N8, a highly pathogenic avian influenza, has become a new zoonotic threat in recent years. As of December 28, 2021, at least 3,206 H5N8 cases had been reported in wild birds and poultry worldwide. In January 2021, a novel virus strain named A/goose/China/1/2021 was isolated during an H5N8 goose influenza outbreak in northeastern China. The PB2, PB1, HA, and M genes of A/goose/China/1/2021 were highly identical to those of H5N8 strains emerging in Kazakhstan and Russia in Central Asia from August to September 2020, while the remaining four genes had the closest homology to those of H5N8 viruses isolated in South Korea in East Asia from November to December 2020. We thus speculate that A/goose/China/1/2021 is likely a reassortant virus that formed in the 2020 to 2021 influenza season and that the migratory birds via the two migration routes of Central Asia and East Asia-Australia may have played an essential role in the genetic reassortment of this virus. The phylogenetic analysis indicated that the HA genes of H5N8 viruses belonging to group II of subclade 2.3.4.4b, including A/goose/China/1/2021, may be derived from strains in Central Asia. Given the complex global spread of H5N8 virus, our study highlights the necessity to strengthen the function of the global surveillance network for H5N8 virus and to accelerate the pace of vaccine development to confront the current challenges posed by H5N8 virus of subclade 2.3.4.4.