Figure 5. Number of amino acid changes along main branches of the tree depicting the phylogenetic relationships between the HA gene segments from A/H1N1 influenza viruses (adapted from Figure 1 with branches within clades collapsed).

The first number represents total number of amino acid changes, with the number following comma referring to the number of amino acid changes occurring in antigenic or potential glycosylation sites. The number in parentheses next to the clade label represents the total number of amino acid changes and those changes at antigenic sites between that clade and the A/New Caledonia/20/1999 vaccine component used from 2000–2001 to 2006–2007.