Swine flu: One killer virus, three key questions

As the world mobilizes against the H1N1 flu pandemic, researchers are working to answer pressing questions about the virus. Brendan Maher visited pathologists at the US Centers for Disease Control and Prevention who are looking at how the virus kills, and a New York laboratory that is testing how it spreads. Declan Butler spent time at a French biosafety level-4 facility where researchers are working out the chances that the pandemic virus will reassort with the H5N1 avian flu virus.