Human infection of H9N2 avian influenza viruses: progress in epidemi-ological research

The zoonoses reports released by World Health Organization and related studies on human AIV H9N2 infection published from 2016 through 2021 were retrieved from PubMed, China National Knowledge Infrastructure (CNKI), WanFang Database (WanFang), and other databases. The risk of human AIV H9N2 infection was evaluated based on serological monitoring results. Attention was paid to genetic causes of across barrier AIV H9N2 infection in the literature study. Based on the studies reviewed, the incidence of human AIV H9N2 infection showed an increasing trend and serological monitoring results showed a high positive rate of environmental and human biological specimens. The mutation of hemagglutinin gene and polymerase gene are of great significance to human AIV H9N2 infection.