Fig. 1. Phylogenetic ML tree of the HA gene segment of human influenza B viruses. The phylogenetic ML tree was inferred from 51 HA nucleotide sequences of both influenza B virus lineages. Bootstrap values of 1000 replicates of ML trees are shown as percentages (values < 70 % are omitted). Bar roughly represents 1 % of nucleotide substitutions between close relatives. Bold type underlined sequences were used in the present study.