[Background] Since the human infection with avian influenza that occurred in Hong Kong in 1997, avian influenza virus has become a major threat to human health and public health.
[Objective] To perform the molecular epidemiological study on a human infection with H10N3 avian influenza.
[Methods] Influenza virus subtyping was detected by real-time quantitative polymerase chain reaction (PCR) method. The virus genome sequencing was completed on the next-generation sequencing platform. Bioinformatics software such as Blasts and Mega 6.1 was used for sequence and phylogenetic analysis.
[Results] In April 2021, a virus was isolated from patients with severe respiratory diseases, which was confirmed as H10N3 subtype avian influenza virus by nucleic acid detection and sequence analysis. A H10N3 subtype avian influenza virus was isolated from the farm product market near the patient’s residence, which was highly homologous with the human isolate. The human isolate was a new gene recombinant H10N3 avian influenza virus, and its HA and NA combination first appeared in poultry in East China in 2019. However, its six internal genes came from H9N2 virus prevalent in poultry in southern China in recent years. The HA cleavage site of the virus contained one basic amino acid R, without insertion of multiple basic amino acids. In theory, it did not belong to highly pathogenic avian influenza virus. The amino acid residue at 228 of HA receptor binding site mutated from G to S, which theoretically enhanced the affinity with human SA-α-2,6 receptor. No E627K mutation of PB2 protein was found, but the amino acid residue at site 591 mutated from Q to K, which theoretically enhanced the adaptability to human body and the pathogenicity.
[Conclusion] This paper reported the molecular epidemiological characteristics of a case of human infection with H10N3 avian influenza virus, and revealed that live poultry market played an important role in gene recombination of avian influenza virus and opportunistic infection.