Epidemiological and genetic characteristics of influenza B virus Victoria lineage in Hubei, 2016−2021

  Objective   To analyze the epidemiological and genetic characteristics of influenza B virus in Hubei province from 2016 to 2021.

  Methods  Based on the reported incidence data of influenza-like illness (ILI) and the etiological surveillance results in Hubei during 2016−2021, 69 strains of influenza B virus were selected to perform whole genome sequencing and bioinformatics software was used to analyze the evolutionary variation characteristics.

  Results  During 2016−2021, a small proportion of influenza B virus Victoria lineage strains in Hubei belonged to the Victoria 1A branch, most strains belonged to the Victoria 1A. 3 branch, which is characterized by deletion of amino acid sites 162–164. Compared with the reference strain, the circulating strain showed multiple amino acid site changes in the key antigenic determinant clusters of the HA protein at the 120 loop, 150 loop, 160 loop and 190 helix, but no neuraminidase inhibitor resistance site variants were found on the NA protein. Only 1 reassortment strain was found in this study.

  Conclusion  Influenza B is mostly seasonal in Hubei province during 2016 to 2021, there were multiple antigenic site mutations in epidemic strains of the Victoria B lineage, however, no mutations in the drug resistance sites were found and need to strengthen influenza surveillance.