Visualizing phylogeographic diffusion. To summarize the posterior distribution of ancestral location states, we annotate nodes in the MCC tree with the modal location state for each node using TreeAnnotator, and visualize this tree using FigTree (available at http://tree.bio.ed.ac.uk/software). To provide a spatial projection, we convert the tree into a keyhole markup language (KML) file suitable for viewing with Google Earth (http://earth.google.com). We introduce the temporal information on the marked-up tree using the TimeSpan KML-function to animate viral dispersal over the time. Example KML files for the Avian Influenza A HA and NA genes are included as supplementary files and software to convert annotated trees to KML is available from the authors on request.