This is a simulation of influenza H3N2 migration dynamics. Each circle represents a virus. Viruses replicate and die and migrate between regions. Viruses accumulate mutations which change their color, thereby representing strain variation. Seasonality is present, so that temperate regions show a summer trough and winter peak in flu incidence. China and Southeast Asia experiences weaker seasonal forcing and because of this they harbor year-round influenza infections. These endemic populations are where new successful variants emerge that eventually take over the entire virus population.
Simulation parameters are taken from Bedford et al. 2010. However, some liberties (like total number of viruses shown) have been taken to promote a visually cohesive display. This is meant as an illustration rather than a research tool.
Click on the animation and press H to bring up a listing of commands.