Discovering the Phylodynamics of RNA Viruses
Figure 2
Phylodynamic patterns of human and avian influenza viruses.
The left diagram shows the phylogeny of the hemagglutinin (HA) gene of human H3N2 influenza A viruses sampled between 1985 and 2005, revealing the “ladder-like” branching structure indicative of antigenic drift. By comparison, the phylogeny of the HA gene of human influenza B virus sampled over the same interval (center diagram) shows the co-circulation of the antigenically distinct “Victoria 1987” and “Yamagata 1988” lineages, as well a shorter length from root to tip, reflecting a lower rate of evolutionary change. Finally, the phylogeny for the HA gene of H4 avian influenza virus (right diagram) reveals the deep geographic division between the Eurasian and Australian versus North American lineages of this virus.