WHO reports Tamiflu-resistant flu in U.S., Canada

Fri Feb 1, 2008 1:44pm EST
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By Stephanie Nebehay

GENEVA (Reuters) - The main seasonal flu virus in the United States and Canada as well as parts of Europe shows higher resistance to the antiviral drug Tamiflu, raising questions about its potential effectiveness in a human bird flu pandemic.

The World Health Organization (WHO) reported the elevated resistance in North America on Friday, but said it was too early to know what the chances may be for increased Tamiflu resistance in the H5N1 strain of avian influenza.

It did not change its recommendation that Tamiflu be used to treat human cases of bird flu.

A number of governments have been stockpiling Tamiflu, made by Switzerland's Roche Holding AG and Gilead Sciences Inc of the United States, for use as a first line of defense in case bird flu sparks a human influenza outbreak.

Health experts fear that the virus, which now mainly affects poultry, could mutate into a form that spreads easily among people and trigger a deadly pandemic.

The WHO said it was investigating the extent of resistance worldwide to Tamiflu, known generically as oseltamivir, in some seasonal H1N1 flu viruses that have a mutation making them "highly resistant."

"The frequency of oseltamivir resistance in H1N1 viruses in the current influenza season is unexpected and the reason why a higher percentage of these viruses are resistant is currently unknown," the WHO said.

The U.S. Centers for Disease Control and Prevention has reported a five percent prevalence of resistance to Tamiflu in samples of H1N1 virus tested. In Canada, 8 out of 128 samples showed resistance, roughly 6 percent, WHO spokeswoman Gregory Hartl said.   Continued...

<p>A Bosnian pharmacist displays Swiss drug maker Roche's Tamiflu bird flu anti-viral tablets at a pharmacy in the capital Sarajevo February 18, 2006. REUTERS/ Danilo Krstanovic</p>