Figure 4From: Long intervals of stasis punctuated by bursts of positive selection in the seasonal evolution of influenza A virusParallel amino acid replacements in H3N2 HA. The replacements in epitope regions are shown in boldface. Color-code for shading of lineages is as in Figure 1. Stasis intervals are indicated in red in the main trunk of the tree, while intervals associated with rapid fitness change appear in green, as in Figure 2.Back to article page