Abstract

Objective In China, H9N2 avian influenza viruses were first reported in chickens in Guangdong province in the mid-1990s. Subsequently, the viruses spread to most regions nationwide, where they became panzootic and endemic. Based on environmental surveillance of live poultry markets in Anhui province from 2013 to 2018, a total of 33 representative environmental isolates were selected and studied systematically. Methods The genomic RNA of Anhui H9N2 isolates was subjected to RT-PCR amplification followed by sequencing analysis. Results Thirty-three strains were isolated from the embryonated eggs of specific-pathogen-free chickens. Phylogenetic analysis indicated that h9.4.2.5-like H9N2 viruses were predominant during 2013--2018 and acquired multiple specific amino acid mutations that may have increased their affinity for mammals and enhanced their infectivity and transmissibility. Additionally, six internal genes of H9N2 clustered together with the novel human-lethal reassortant viruses, such as low pathogenicity H7N9, H10N8 and Anhui H5N6 viruses, and even HPAI H7N9. Conclusion Because H9N2 viruses may be the donors of internal genes that lead to the generation of novel reassortant viruses with enhanced pathogenicity in Anhui province, continuous environmental surveillance of live poultry markets, a key source of reassorted H9N2 and other avian influenza viruses, is of great importance.