Figure 3. Phylogenetic tree of influenza A H1N1 and H1N2 virus HA1 nucleotide sequences. The tree was generated by using joining-joining analysis. The lengths of the horizontal lines are proportional to the number of nucleotide substitutions per site. Trees were bootstrapped x100. H1N2 viruses are indicated with an asterisk. The current H1N1 vaccine strain is in bold typeface.
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