Evolution and spread of H8Nx avian influenza viruses from wild birds in East Asia, 2019-2024.

Subtype H8 avian influenza viruses (AIVs) are rarely reported and poorly characterized. We isolated nine H8Nx AIVs from wild birds in South Korea during 2019-2024. Whole-genome and phylogenetic analyses showed close relationships with Asian AIVs and frequent reassortment with other low pathogenic avian influenza viruses (LPAIVs). Time-scaled analysis indicated recent introductions of North American lineage viruses into South Korea, despite long-term independent evolution of Eurasian and North American lineages. Amino acid substitutions linked to mammalian adaptation were also found. These findings provide baseline data for continued H8 AIV surveillance in wild birds.