Genetic variation in the hemagglutinin of A(H1N1) 09pdm and A(H3N2) influenza viruses in the Beijing area from 2009 to 2014.

BACKGROUND

A(H1N1) 09pdm and A(H3N2) influenza viruses are the main cause of occasional influenza pandemics and seasonal influenza epidemics around the world. Unfortunately, the understanding of long-term genetic variation in these viruses remains limited.

METHODS

In this study, hemagglutinin genes from 90 A(H1N1) 09pdm and 48 A(H3N2) influenza viruses in the Beijing area from 2009 to 2014 were sequenced and analyzed.

RESULTS

The hemagglutinin genes in A(H1N1) 09pdm and A(H3N2) shared nucleotide similarity that ranged from 93.06% - 99.88% and 98.68% - 99.29%, respectively, compared with current vaccine strains. 10 and 7 amino acid mutations in antigenic sites were identified in these two strains, respectively. In addition, a new site 177 glycosylation, which did not exist in previous circulating strains, was identified in 3 A(H1N1) 09pdm isolates.

CONCLUSIONS

This study demonstrated the continued evolution of seasonal influenza viruses in the Beijing area, indicating that an update of the vaccine is needed, especially for A(H1N1) 09pdm influenza virus.