Figure 2. Phylogenetic trees of the HA and NA gene segments of highly pathogenic avian influenza virus A(H5N6) isolated in Japan. The nucleotide sequences of the H5 HA (A) and N6 NA (B) genes were analyzed by the maximum-likelihood method along with the corresponding genes of reference strains using MEGA 7.0 software (http://www.megasoftware.net/). Horizontal distances are proportional to the minimum number of nucleotide differences required to join nodes and sequences. Numbers at the nodes indicate the probability of confidence levels in a bootstrap analysis with 1,000 replications. Gray indicates viruses isolated in this study; underlining indicates viruses isolated in humans. The H5 HA gene sequences are classified into genetic clades as defined by Lee et al. (9). Scale bars indicate nucleotide substitutions per site. HA, hemagglutinin; NA, neuraminidase.