Characterization of a novel H3N2 influenza virus isolated from domestic ducks in China

Cases of human infection with a novel H7N9 avian influenza virus (AIV) were first reported in March 2013, which caused 115 deaths within a single year. Beyond that, other subtypes of H7 AIV were isolated from poultry in eastern China during the same period, including H7N7 and H7N2 AIV. In the present study, a subtype H3N2 AIV was isolated from ducks from Anhui Province, China. Sequence and phylogenetic analyses revealed that seven gene segments of this virus showed the highest sequence homology with that of the H7 subtype influenza virus, which is presumed to be the reassortants of the H3 and H7 subtypes AIV. The present study also reconfirmed that the reassortment between the H7 subtype and waterfowl-originating AIVs universally occurred in waterfowl. Animal inoculation tests showed that the virus has low pathogenicity in chickens; however, it could be replicated in the lungs of mice. The emergence of this H3N2 isolate emphasizes the importance of enhancing the surveillance of waterfowl-originating AIVs, the identification of novel reassortant strains, and characterization of their biological properties.