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Is It H1N1 Swine Flu, Doc?

H1N1 Swine Flu Driving Surge in U.S. Doctor Visits
WebMD Health News
Reviewed by Louise Chang, MD

May 11, 2009 -- The H1N1 swine flu has caused a surge in doctor visits for flu-like symptoms -- and now about a third of flu cases are infections with the new flu bug.

Fortunately, the most troubling sign of a bad flu epidemic -- an unusual rise in deaths due to flu or pneumonia for a given time of year -- hasn't yet occurred.

Swine Flu Outbreak: Get the Facts

Swine Flu Slideshow

Learn more about the H1N1 swine flu and see what you can do to stay healthy.

View the slideshow.

But that may change in a hurry as the new flu continues its spread in communities across the U.S.

Last weekend, the H1N1 swine flu killed a 30-something Washington state man with an underlying heart condition. As of today, there are 3,300 probable and confirmed cases in 48 states and the District of Columbia, with 94 hospitalizations.

And that number is only the "tip of the iceberg," the CDC's Anne Schuchat, MD, said today at a news conference. The virus is spreading so widely, Schuchat said, that soon the U.S. will be unable to count individual cases.

"I believe the numbers we report are a minority of actual infections," Schuchat said. "The way we will be tracking in the future will be ... to put into context how much of the flu we are seeing is due to the new strain. That will be our priority in the fall, and during the flu season in the Southern Hemisphere, to see if this new virus is taking hold or just fizzling out or changing its properties."

What the CDC will track is flu trends. And the new flu is making an impact on these trends. Already, 2.6% of doctor visits are for flu-like illness, above the national baseline.

Not surprisingly, doctors have been sending a lot more samples to state labs for flu testing. That led to a big spike in confirmed flu cases in the week ending May 2, the most recent week in the CDC data.

That week, about 13% of flu tests were positive for flu:

  • 33% of positive tests were either confirmed or probable type A H1N1 swine flu.
  • 18% of positive tests were seasonal type A H1N1 virus.
  • 16% of positive tests were seasonal type A H3N2 virus.
  • 16% of positive tests were type A viruses not further subtyped.
  • 17% of positive tests were type B flu bugs.

Those who do go to their doctor with flu-like symptoms won't have to wait for the test results. People who are seriously ill, or those with risk factors or underlying conditions that put them at risk of bad outcomes, will get treatment with Tamiflu or Relenza. Doctors will keep an eye on healthy people with mild symptoms but likely will not treat them with antiviral drugs, as most people recover fully from the new flu in a week or so.

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