Vaccine immunity toughens Swine flu fight By STACEY SINGER
Palm Beach Post Staff Writer
Wednesday, October 28, 2009
A half of a percent of U.S. swine flu samples are now proving resistant to Tamiflu, the CDC says, and the newly available drug Peramivir is unlikely to help those cases.
Dr. Philip Peters, a medical officer with the Centers for Disease Control and Prevention's 2009 H1N1 Influenza Task Force, said drug resistance has been "sporadic," and mostly in people who were immuno-suppressed and not able to completely clear their infection.
"But there is no evidence of community-wide resistance," Peters told medical providers in a conference call this week.
To date, nine cases of Tamiflu resistance have been found out of 1,000 U.S. cases studied, he said. There was an eightyfold reduction in sensitivity to Peramivir in flu virus samples that didn't respond to Tamiflu.
"We would not recommend using this in resistant strains," he said.
The CDC is recommending Tamiflu or Relenza for all hospitalized patients who appear to have flu, even if the rapid test for it is negative.
Doctors are finding that the rapid test is producing so many false negatives that it's not useful.
"At this point we're not even swabbing people anymore," said Dr. Larry Bush, chief of infectious disease at JFK Medical Center in Atlantis.
Jupiter Medical Center's Dr. Leslie Diaz said she still swabs, but considers the test inconclusive if it comes back negative.
"If you rely on that you may lose the opportunity to treat," said Diaz, an infectious disease specialist. "When a patient is sick enough, and you do the flu swab and it's negative, and you still suspect flu, you treat the patient. You don't rely on the swab."
Swine flu has hospitalized 74 people in Palm Beach County since the outbreak began, and seven deaths have been associated with it. On Wednesday, county health officials announced the seventh death, in a 46-year-old woman who was not hospitalized.
Until last week, doctors had just two antiviral drugs to choose from to treat swine flu: Tamiflu or Relenza. On Friday, the FDA issued an emergency use authorization for Peramivir, and soon after, five hospials requested it. That's because it can be given intravenously.
Tamiflu is an oral drug, given as a pill or a liquid. Relenza is a mist, breathed in through a disk-shaped inhaler. The drugs have been lifesavers in many cases, the CDC's Peters said.
But there have been some patients who are so sick that they cannot practically take either medication. In that case, doctors may request Peramivir, Peters said.
The drug works much like Tamiflu and Relenza, by preventing infected cells from releasing viral copies.
It appears to have a range of side effects similar to Tamiflu and Relenza, as well, he said. Those include diarrhea, nausea, vomiting and neutropenia, a problem producing certain white blood cells.
So far, just 1,891 people have participated in clinical trials on the new antiviral, and only 33 of them received the drugs for five days or more. No pregnant women or children were part of the trial.
"We know that when drugs are used more widely than in clinical trials, additional adverse events are observed," Peters said.
Diaz said that's not a large enough sample to make her feel comfortable administering the new drug.
"I don't think we know enough about this drug," she said.
Bush, at JFK, said he was pleased to have another formulation.
"I think, in someone who is critically ill and is going to die, we are willing to pull out all the stops," Bush said
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