Figure 2

Four major global transmission routes of clade 2.2H5N1 avian influenza. Each color represents a single route with its corresponding key regions. Colored patches show regions that have larger genetic distances along the route. Three probable sources, namely, Russia, Mongolia and the Middle East (Kuwait and Saudi Arabia) in three consecutive years (2005, 2006 and 2007), are indicated by a red, ring-shaped symbol.