A flu virus is a powerhouse of evolution, mutating at the maximum speed nature allows. A mild virus can morph into a killer and vice versa. One change already made this year's swine flu more of a problem, helping it spread more easily among people. The big ...

No matter what you call it, leading experts say the virus that is scaring the world is pretty much all pig. So while the U.S. government and now the World Health Organization are taking the swine out of "swine flu," the experts who track the genetic heritage ...