Genetic Characterization of Continually Evolving Highly Pathogenic H5N6 Influenza Viruses in China, 2012–2016

H5N6 highly pathogenic avian influenza is a zoonotic disease that causes recurring endemics in East Asia. To date, at least 155 outbreaks have been reported in China, including 15 human infection cases. The repeated outbreaks increase the concern that H5N6 viruses may spill over to humans and cause a pandemic. In February, 2016, some peafowls in a breeding farm suffered from a highly contagious disease. Based on post-mortem examination, RT-PCR detection, and virus isolation, we confirmed that highly pathogenic H5N6 influenza virus was the causative agent, which was named as A/Pavo Cristatus/Jiangxi/JA1/2016. Animal experiments displayed highly pathogenicity for chickens, and the estimated median lethal dose for mice was ~104.3 TCID50. Phylogenetic analysis showed that JA1/2016 were clustered into H5 clade 2.3.4.4. Furthermore, we find that H5N6 influenza viruses were classified into two groups: group 1 and group 2.Group 2 influenza viruses can not been detected since the end of 2014. While group 1 influenza viruses continually evolve, and reassortant with the “gene pool” circulating in South of China, giving rise to novel subtype of influenza viruses. The increasing number of hosts, expanding range of distribution, and continually evolution of H5N6 AIVs enhance the risk that H5N6 viruses may spread to other continents of the world and cause a pandemic.