Surveillance of avian influenza viruses (AIVs) in live poultry markets across China (2019–2023) found 17.57% of 18,425 samples were AIV-positive, with H9N2 being the dominant. An automated H9N2 clade nomenclature system was proposed, uncovering ten sub-subclades cocirculated with antigenic variation. Most H9N2 possessed HA-L226 (human-receptor-binding) and NP-N52 (human MxA-resistance) and H9N2 with these mutations preferred human-type receptors and increased replication in human cells. H9N2 containing HA-L226, PB2-V/K627, and NP-N52 transmitted between guinea pigs and ferrets through direct and aerosol transmission, highlighting zoonotic risk concerns.
Jun 03, 2025