In this episode, we'll hear parts of three talks from the recent symposium, Exploring the Dynamic Relationship Between Health and the Environment, organized by the American Museum of Natural History's Center for Biodiversity and Conservation. Speakers include Penn State's Peter Hudson, who talks about disease transmission; Oxford's Oliver Pybus, on how genome analysis exonerated health care workers accused of infecting children with HIV; and N.Y.U.'s Martin Blaser on our disappearing stomach flora. Plus, we'll test your knowlege of some recent science in the news. Web sites related to this episode include www.symposia.cbc.amnh.org/health