Figure 2

Phylogenetic analysis of the HA genes of the H5Nx viruses. To investigate the origins of novel influenza A (H5N6) viruses isolated from 2017 to 2019, full-length nucleotide sequences of the HA gene were compared with those in selected representative isolates obtained from the National Center for Biotechnology Information (NCBI) and EpiFlu database of the Global Initiative on Sharing All Influenza Data (GISAID). The sequences of novel influenza A (H5N6) viruses are listed in Supplementary Table 1. Phylogenetic analysis was inferred by the maximum likelihood (ML) method based on the Tamura-Nei model by using the Molecular Evolutionary Genetics Analysis version 10 (MEGAX). Red arrows represent the H5N6 viruses isolated in 2017 and 2019. Blue arrows represent the H5N6 viruses isolated in 2018. Group A of clade 2.3.4.4 viruses comprised influenza A (H5N8) viruses identified in South Korea during 2014 and 2015. Group B of clade 2.3.4.4 viruses comprised H5N6 and H5N8 viruses identified in China, South Korea, Japan, and Europe during 2014 and 2018. Group C of clade 2.3.4.4 viruses comprised H5N6 viruses identified in Japan, China, and South Korea during 2015 and 2018. CL: clade; EM: environment; DK: duck; WD: wild duck; WS: whooper swan; JC: jungle crow; CO: coot; CK: chicken; CT: common teal; FL: feline; NS: Northern shoveler; FP: ferruginous pochard; GS: goose; BT: baikal teal; MD: mallard; BD: broiler duck; Brk: breeder duck; MS: mute swan; TD: tufted duck; EHG: Eurasian herring gull; PC: peacock; GF: guineafowl; BC: brahma chicken; GBG: great black-backed gull; Bck: black chicken; Msdk: muscovy duck; Mddk: mandarin duck; BHGS: bar headed goose; BB: blackbird.