A new strain of swine flu has shown up in two children in Pennsylvania and Indiana who had direct or indirect contact with pigs. The virus includes a gene from the 2009 pandemic strain that might let it spread more easily than pig viruses normally do.
So far, there's no sign that the virus has spread beyond the two children, the Centers for Disease Control and Prevention reported Friday.
"We wanted to provide some information without being alarmist," because people have contact with pigs at fairs this time of year and doctors should watch for possible flu cases, said Lyn Finelli, the CDC's flu surveillance chief. "We're always concerned when we see transmission of animal viruses to humans."