"The lack of some of the factors that have been associated with more severe disease in previous pandemics, we are not seeing those." Testing for the virus is also becoming faster, Besser said. And, he added, "The situation in Mexico is. "And that's encouraging information." In addition, some of the initial lab tests are heartening, Besser said. And, while insisting that "we are not out of the woods," Dr. "We have distributed test kits to every state and this will allow for more rapid diagnosis at the state level," he said.

"So far the severity of illness we are seeing in this country is very similar to what we see with seasonal flu," Besser said. Eliot Besser, acting director of the U.S. -- The number of confirmed swine flu cases in the United States climbed to 286 in 36 states. Centers for Disease Control and Prevention, said during an afternoon teleconference that "we are seeing a lot of encouraging signs." Among the encouraging signs.

But, the revised numbers indicate catching up on a backlog of lab tests, and not a sudden rise in new infections, federal health officials said.