Characteristics of influenza A (H3N2) virus hemagglutinin genes in Fujian province from 2014 to 2016
Objective 
To investigate the genetic characteristics and mutations in hemagglutinin (HA) genes of influenza A subtype H3N2 viruses isolated in Fujian province during 2014—2016. 
 
 
Methods 
HA gene fragments of 44 randomly selected influenza A (H3N2) viruses were amplified by RT-PCR and then sequenced by Sanger sequencing. Obtained sequences were analyzed by bioinformatics software and online websites. 
 
 
Results 
Pair-wise similarity among HA genes of the 44 strains was between 97.3%-100.0% at nucleotide level. The average variations between epidemic strains and corresponding vaccine strains in the year of 2014, 2015 and 2016 were 0.012, 0.008 and 0.009, respectively. The genotype of epidemic strains in 2014 was 3C.3a rather than 3C.1 of the vaccine strain. Notably, variations at some antigenic sites, receptor binding sites (RBSs) and N-Glycosylation sites were identified despite the fact that the genotypes were identical between epidemic and vaccine strains in 2015 and 2016. 
 
 
Conclusion 
Variations at the HA genes of influenza A (H3N2) viruses in Fujian province occurred during the year of 2014—2016, reflecting the ability of circulating strains to escape the vaccine-induced immunity. Sustainable influenza surveillance and prompt identification of viral variants would benefit influenza prevention and control. 
 
 
Key words: 
Influenza A subtype H3N2; Hemagglutinin (HA); Genetic characteristic; Mutation