Genetic variation and phylogenetic analysis of hemagglutinin genes of H9 avian influenza viruses isolated in China during 2010-2012.

Genetic variation and phylogenetic relationships of H9 avian influenza viruses (AIVs) were analyzed based on hemagglutinin (HA) gene sequences of 84 Chinese H9 reference viruses recently available in GenBank, 3 widely used vaccine strains and 29 novel isolates. The novel isolates were obtained from vaccinated poultry flocks in 11 provinces of China during 2010 to 2012. The nucleotide homologies of HA genes of these isolates ranged from 87.