ananyo writes "With Taiwan announcing the first case of H7N9 avian flu outside mainland China, researchers have revealed how the virus may spread in China — and beyond. The projections use risk maps developed for human infection by another, well-established avian flu — H5N1. Indeed, when human cases of H7N9 are overlaid on a risk map, they appear to fall within the highest risk areas for H5N1. The map suggests that high-risk areas for H7N9 might include Shandong province (where the first case was reported 23 April) and a belt extending around the Bohai sea to Liaoning province in the north. Though there has been no evidence of sustained human-to-human spread of H7N9 so far, researchers have analyzed airline passenger data for China. Eastern China — the epicenter of the current the H7N9 outbreak — is one of the world's busiest hubs for airline traffic. From the Nature story: 'A quarter of the global population outside of China lives within two hours of an airport with a direct flight from the outbreak regions, and 70% if a single connecting flight is included.'"