If people actually reduce social contact and cut down on air travel and stay home in response to a single cough, then it’s much likelier that swine flu will quickly die out. If it does, we’ll all feel a bit foolish over having taken those precautions and late night comics will make fun of Joe Biden and everyone will move on. If we don’t, and R jumps up, then we could be dealing with a full blown pandemic and Biden’s warning will come to be seen as, if anything, insufficiently alarmist.
R is the reproduction rate. Interesting insight — go read what he has to say, it’s only a half-dozen paragraphs.