Multiple viral introductions: molecular characterization of influenza B virus in Wenzhou, Zhejiang, China, from 2011 to 2014 based on hemagglutinin and neuraminidase genes.

Influenza B virus is a major causative agent of respiratory disease in humans. Our study of an outbreak of influenza B virus in Wenzhou from 2011 to 2014 revealed that 163 (5.58 %) of 2921 samples were influenza B positive. Sequencing of the hemagglutinin and neuraminidase genes showed substitutions at the amino acid level. Phylogenetic analysis revealed co-circulation of the B/Victoria and B/Yamagata lineages in the Wenzhou area from 2011 to 2014. Multiple viral introductions from both Chinese and international sources played important roles in endemic co-circulation and transmission in coastal southeastern China. Electronic supplementary material The online version of this article (doi:10.1007/s00705-015-2721-7) contains supplementary material, which is available to authorized users.