RESUMEN
Objective To analyze the prevalence of influenza A (H3N2) virus in Hangzhou be-tween 2012 and 2017 and to investigate the genetic variations in hemagglutinin ( HA) and neuraminidase ( NA) . -ethods Throat swab samples were collected for viral isolation from 12185 patients with suspected influenza in Hangzhou area from January 2012 to December 2017. Influenza virus subtypes were identified by real-time RT-PCR. HA and NA genes of some isolated Influenza A (H3N2) viruses were amplified with spe-cific primers and then analyzed by sequencing and phylogenetic analysis. Results Influenza A (H3N2) virus was the predominant subtype circulating in Hangzhou during 2012 to 2017. It caused high morbidity in elderly people (Z=81. 039, P<0. 05). Most of the isolated influenza A (H3N2) viruses belonged to the phylogenetic clades of 3C. 3a and 3C. 2a. These viruses shared a homology of 96. 7％-100％ in nucleotide sequences of both HA and NA genes, but possessed several HA and NA mutations in antigenic sites. Con-clusions Influenza A (H3N2) virus was an important pathogen causing influenza epidemics in Hangzhou during 2012 to 2017. HA and NA genes showed many mutations in antigenic sites. No drug resistant virus was reported.