Laurie Garrett on Late Night Live again just now. She says we have two things to worry about with this virus.
Firstly, H1N1 and H5N1 get mixed up in a host (is that the right word?). That is, a person or a pig or a chicken catches both strains of flu at the same time. This is now a possibility given that H1N1 is hitting geographies where H5N1 is endemic. In that situation you risk mixing strains to get a new nasty strain. A new strain that has the virulence of H5N1 (which has killed 80%+ of the people who have contracted it in Indonesia) and the contagiousness of H1N1.
The second thing to worry about is if the current swine flu mixes with another H1N1 strain currently circulating in North America that is resistant to Tamiflu.