The severity of cases in the current swine flu outbreak has varied widely, from mild cases to fatalities. Early cases in the U.S. were mild, but there has been at least one U.S. death from swine flu. And it's impossible to know whether the virus will change, either becoming more or less dangerous. Scientists are watching closely to see which way the new swine flu virus is heading -- but health experts warn that flu viruses are notoriously hard to predict, as far as how and when they'll change.
