Epidemiological and evolutionary analysis on influenza A (H3N2) virus in Hubei, 2017–2020

  Objective  To investigate the epidemiological distribution and gene evolution of influenza A (H3N2) virus in Hubei province from 2017 to 2020.

  Methods  Based on the influenza etiological surveillance data in Hubei, the epidemiological distribution of influenza A (H3N2) virus in Hubei during 2017–2020 was analyzed. A total of 38 strains of influenza A (H3N2) virus sent by the influenza surveillance network laboratories in Hubei during 2017–2020 were selected for gene sequencing according to the annual distribution and area distribution. The amino acid sequences of HA and NA were obtained and their antigens were analyzed, the changes of amino acid sites in clusters were analyzed, and gene evolution and 3D modeling analyses were conducted.

  Results  There were three detection peaks of influenza A (H3N2) virus in Hubei from 2017 to 2020. The first peak was predominated by 3C.2a1 virus cluster, the second peak was predominated by 3C.2a1b+T131K virus cluster and the third peak was predominated by 3C.2a1b+T135K virus cluster. 3C.2a1b +T131K virus cluster and 3C.2a1b+T135K virus cluster had 8 different amino acid mutation sites on 3 antigenic determinants of HA protein. There were significant differences among sites 50, 131, 135, 140 of 3C.2a1b+T131K virus cluster and 3C.2a1b+T135K virus cluster in the three-dimensional simulation structure diagram.

  Conclusion  The cluster of influenza A (H3N2) virus in Hubei evolved continuously from 2017 to 2020. Enhancement of evolutionary surveillance and antigen mutation analysis of the recent cluster of 3C.2a1b+T135K virus would improve the epidemiological and gene evolution surveillance of influenza viruses in Hubei.