Figure 2.

Phylogenetic trees comparing the neuraminidase nucleotide sequences of novel influenza A(H5N6) viruses, South Korea, December 2017 (n = 4)

Bdk: broiler duck; BG: barnacle goose; Brk: breeder duck; BT: baikal teal; CK: chicken; CT: common teal; DK: duck; EHG: eurasian herring gull; EM: environment; FP: ferruginous pochard; GBG: great black backed gull; GH: grey heron; GS: goose; MD: mallard; Mdk: mallard duck; MS: mute swan; NA: neuraminidase; NS: northern shoveler; PC: peacock; PS: painted stork; RS: ruddy shelduck; SB: spoonbill; TD: tufted duck; WD: wild duck.

To investigate the origins of our novel influenza A(H5N6) viruses (A/AP/Korea/W612/2017, A/AP/Korea/W613/2017, A/AP/Korea/W614/2017 and A/AP/Korea/W615/2017: marked with asterisks), full-length nucleotide sequences of NA genes were compared with available H5Nx and high blast scoring virus sequences from the GenBank and Global Initiative on Sharing All Influenza Data (GISAID) databases; GISAID sequences are acknowledged in Supplement 1. The deposited GenBank accession numbers of NA genes are MG891812-MG891815.Time-scaled phylogenies (dates shown on the horizontal axis) were inferred using strict-clock Bayesian Markov Chain Monte Carlo analysis. The month of isolation is indicated at the end of the virus name.

The yellow line indicates the 2016/17 influenza A(H5N6) viruses while the blue line indicates the 2017/18 H5N6 viruses that were isolated from South Korea. The Group A of clade 2.3.4.4 viruses comprises influenza A(H5N8) viruses identified in South Korea in the 2013/14 and 2014/15 winter seasons. Group B comprises H5N8 and H5N6 viruses identified in Asia and Europe during the 2013/14 to 2017/18 winter seasons. Group C of clade 2.3.4.4 viruses comprises H5N6 viruses identified from China in the 2015/16 and South Korea in the 2016/17 winter seasons, respectively.