A common strain of influenza circulating in
the United States this winter is resistant to Tamiflu, the most popular drug
used to treat it, federal health officials said on Friday.
The situation poses little danger, according to the U.S. Centers for
Disease Control and Prevention, because Tamiflu is only used in a minority of
cases. It advised doctors to use rival drug Relenza or rimantadine, an older
drug.
Forty nine out of 50 samples tested resist the drug, although they can
still be treated with other flu medications, the CDC said in a special advisory
to doctors.
"It is still very early in the season. There is very little influenza out
there," CDC Director Dr. Julie Gerberding told reporters in a telephone
briefing.
"This is probably actually not going to affect very many people because
we don't use a lot of antiviral drugs in our country," Gerberding said. "Most
people with influenza don't get any treatment."
In a normal flu season, three strains of flu circulate called H1N1, H3N2
and influenza B. Flu kills about 36,000 Americans in an average year.
It is the H1N1 strain that is turning up resistant samples, Gerberding
said, and comes mostly from Hawaii, Massachusetts and Texas, the states with the
most cases of influenza.
Last year, just under 11 percent of the H1N1 samples tested were
resistant to Tamiflu. Gerberding said she did not think the virus had evolved,
but that the strain that happened to pop up was also resistant to the drug.
"We can't predict whether or not these strains will end up being the most
important strains in this year's flu season. This particular H1N1 could fizzle
out," Gerberding said.
Tamiflu, known generically as oseltamivir and made by Roche AG and Gilead
Sciences Inc., can both prevent and treat flu if taken quickly enough.
A similar drug is Relenza, or zanamivir, made by GlaxoSmithKline under
license from Australia's Biota Inc..
The U.S. national stockpile of antivirals is about 80 percent Tamiflu and
20 percent zanamivir, according to the Health and Human Services Department. The
CDC's Dr. Tim Uyeki said this season's development illustrated the need to keep
a diversified array of drugs on hand.
"But zanamivir ... is not approved for those less than 7 years old,"
Uyeki said. People with asthma are also advised not to use the drug, which is
inhaled.
Gerberding noted that this year's flu vaccine matched the three strains
circulating so far very well. The CDC says there is still time for Americans to
get a flu shot, as the season usually peaks in February.
The CDC and the U.N. World Health Organization are concerned about the
threat of a a new and deadly strain of flu developing that would sweep the
world. That is one reason to keep a stockpile of antivirals handy, CDC says,
although this year's flu season appears to be mild.
(Editing by Alan Elsner and Will Dunham) Keywords: FLU TAMIFLU/
(Maggie.Fox@Reuters.com; 1 202 898 8492)
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