Comparative analysis of influenza A (H7N9) virus genomes in human infection cases in Gansu

  Objective  To analyze the sequence of avian influenza A (H7N9) virus detected in human infection cases in Gansu, compare the genetic variation and molecular evolution characteristics of highly and low pathogenic H7N9 viruses, and provide scientific reference for the prevention and control of human infection with avian influenza virus.

  Methods  The genomes of H7N9 virus found in Gansu since 2017 were compared, and the whole genome characteristics were analyzed by MEGA 7.0 and other software.

  Results  The 6 cases of human infection with H7N9 virus had history of live poultry or environmental exposures, and 3 virus strains were isolated, i.e. GS/19545, GS/27151 and GS/23275. The HA and NA genes of GS/19545, GS/27151 and GS/23275 were all from the Yangtze River Delta Branch of Eurasia. The NP gene of GS/23275 was in the same evolutionary branch with the highly pathogenic H7N9 virus from Guangdong in 2017, forming another distinct branch differed with the low pathogenic strains of GS/19545 and GS/27151. The results showed that the PB2 gene of GS/23275 was closely related to the H9N2 virus isolated from poultry in Anhui in 2015. G186V and S138A mutations occurred in HA receptor binding sites of three H7N9 strains, 68–72 amino acid deletion occurred in NA protein stems, and the same amino acid mutation occurred in PA, PB1, PB2, M1, M2, NS1, NS2 proteins.

  Conclusion  Some important molecular mutations occurred in the genome of H7N9 virus detected in human infection cases in Gansu, which might lead to increased virulence of avian influenza virus and potential interpersonal transmission. Strengthening the research and analysis on the genetic characteristics of avian influenza virus might facilitate the surveillance for the mutation of the virus at molecular level and carry out effective prevention and control of the epidemic.