Wild birds are the primary natural reservoirs for avian influenza virus (AIV), and waterfowl and shorebirds (order Anseriformes and Charadriiformes) are particularly affected. The wild bird associated HPAI viruses have resulted in continuous outbreaks with devastating economic loss in the poultry industry and severe threat to public health. The recent spread of Asian-origin HPAI subtype H5N1 into Europe and Africa has put an increased focus on wild bird-associated AIV transmission.

AIV can be genetically distinguished by geographical origin. The present study found evidence of intercontinental transfer of North American lineage AIV into Asia via migratory bird populations. The North American lineage genes were detected in live bird markets during avian influenza surveillance, seemed to have reassorted with Eurasian AIV in wild bird habitats, and had transmitted to live bird markets. Unlike most Asian isolates, these viruses contained North American lineage genetic segments which clustered with Alaskan low pathogenic AIVs in phylogenetic analyses. Enhanced AIV surveillance is required to understand the influence of newly transferred North American lineage AIV genes on AIV evolution in Asia and to investigate AIV ecology in various transcontinental migrant species.