Novel variants of clade 2.3.2.1 H5N1 highly pathogenic avian influenza virus in migratory waterfowl of Hongze Lake

Wild birds are known to play a major role in the evolution, maintenance, and spread of the avian influenza viruses (AIVs). More specifically, the waterfowl are thought to be the natural reservoirs of AIVs. Here, we conducted a survey in 2015 at the Hongze Lake and characterized 11 H5N1 highly pathogenic AIVs isolated from wild waterfowls which were found to belong to clade 2.3.2.1. In contrast, the 11 variants of H5N1 viruses did not align with the three previously defined monophyletic subclades. Antigenicity analysis revealed that antigenic drift occurred in these H5N1 variants. Hence, current vaccines may fail to confer protection against the H5N1 AIV variants in poultry.