U.S. health officials are seeing a surprisingly high number of cases of ordinary, seasonal flu at a time when the flu season typically peters out.
About half of all people who test positive for the flu have the new swine flu virus, Dr. Daniel Jernigan of the federal Centers for Disease Control and Prevention said Friday.
The rest have seasonal flu, which is still causing widespread or regional illness in about two dozen states, "something that we would not expect at this time," he said. "We would be expecting the season to be slowing down or almost completely stopped."
The higher numbers of seasonal flu cases do not seem to be just because health officials are looking harder this year because of worries about swine flu, Jernigan said. A network of doctors who track how many patients are coming in with flulike symptoms, plus evidence from school outbreaks and lab testing, points to more flu — not just more reporting, he said.
In the United States, there are now over 4,700 probable and confirmed cases of swine flu, and five deaths.
"The H1N1 virus is not going away," Jernigan said. The virus "appears to be expanding throughout the United States" and poses "an ongoing public health threat," he said.
Swine flu continues to affect more younger people — those ages 5 to 24 — and CDC is still seeing relatively few cases in older people.
"That may be just a matter of time" until the virus spreads to that population, or it may prove to be a difference in the virus or its effect on various groups, he said.
Officials are still monitoring the situation in Mexico, where the outbreak began. However, the CDC's quarantine chief, Dr. Martin Cetron, said the agency soon would downgrade its warnings about travel to Mexico. The CDC had urged people to avoid nonessential travel to that country, but that will be changed to just a precaution for people at high risk of flu complications.