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. Both children recovered.
"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." People rarely get flu from pigs — only 21 cases have been documented in the past five years — and it's too soon to know how infective this virus will be, she said.
The new strain is a hybrid of viruses that have infected pigs over the past decade and a gene from the H1N1 strain that caused the pandemic two years ago. It is the first combination virus to turn up in people since the pandemic, said Michael Shaw, a lab chief at the CDC. It's classified as an H3N2 virus.
The first case was an Indiana boy under age 5 who was sickened in late July. He had no contact with pigs, but a caretaker did in the weeks before the boy fell ill. The second case was a Pennsylvania girl, also under age 5, who had contact with pigs at an agricultural fair last month. Health officials are investigating reports of illness in other people who went to the fair. No additional cases have been confirmed. The viruses in the two children were similar but not identical.