Looks like H1N1 virus, still more popularly known as the swine flu, is waning in Mexico. The virus has sickened at least 245 people in the U.S., and killed a young boy. So what lies ahead? Obviously no one (except maybe psychic John Edwards) knows for sure, but some disease trackers are mapping a possible course. How? Well, a computer simulation out of Northwestern University is taking inspiration from an unusual source: the dollar bill. Donald McNeil Jr, Science reporter for our partner, The New York Times, joins The Takeaway with a look at how the virus might spread in the U.S.