Genetic evolution of avian influenza A(H9N2) viruses from poultry markets in Guangzhou, 2017–2019

ObjectiveTo analyze the characteristics of genetic evolution of avian influenza A (H9N2) virus strains isolated in Guangzhou and provide research data for the prevention and control of human infection with avian influenza virus.

MethodsA total of 24 strains of H9N2 virus isolated from the samples collected in poultry markets in Guangzhou were randomly selected for sequencing. The genetic evolution characteristics of the strains were analyzed with bioinformatics software.

ResultsThe nucleotide homology of all the strains ranged from 86.20% to 100.00%, and the evolutionary distance of nucleotide was 0.00–1.54. Genetic evolution analysis showed that all the strains clustered into same phylogenetic clades, and belonged to genotype G57. Molecular analysis showed that all the strains belonged to low pathogenic avian influenza viruses, and all strains had Q226L mutation in HA receptor binding sites, which suggested that these viruses can easily recognize the receptor of human. Most of the strains had mutations related to enhanced pathogenicity at the sites of HA-N166D, PB2-L89V/292V, PB1-I368V, L473V, PA-K356R, S409N, M1-N30D, T215A, NS1-P42S. All the strains were sensitive to neuraminidase inhibitors and resistant to alkylamines.

ConclusionAvian influenza A (H9N2) viruses circulated in Guangzhou during 2017–2019 belonged to genotype G57, which had stable variation of enhanced binding ability to human receptor. Most of the strains had mutations of enhanced pathogenicity, which needed to be monitored continually.