The U.S. Centers for Disease Control and Prevention said Friday it was too late to contain the swine flu outbreak in the United States.
CDC acting director Dr. Richard Besser told reporters in a telephone briefing it was likely too late to try to contain the outbreak, by vaccinating, treating or isolating people.
"There are things that we see that suggest that containment is not very likely," he said.
He said the U.S. cases and Mexican cases are likely the same virus. "So far the genetic elements that we have looked at are the same."
But Besser said it was unclear why the virus was causing so many deaths in deaths in Mexico and such mild disease in the United States.