WHO reports some Tamiflu-resistant flu in U.S.

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Fri 1 Feb 2008, 11:04 GMT

[-] Text [+] GENEVA, Feb 1 (Reuters) - The main influenza virus circulating in the United States has shown raised resistance to Roche Holding Ag's Tamiflu, already found to be less potent in parts of Europe, the World Health Organisation (WHO) said on Friday.

The WHO said that until further study was done, it was too early to know what if any potential there might be for such an increase in resistance to Tamiflu to occur in H5N1 bird flu viruses. The agency was not changing its recommendation Tamiflu be used for prevention and treatment of human bird flu. The WHO said it was still investigating the extent of resistance worldwide to Tamiflu, known generically as oseltamivir, in some H1N1 viruses which have a mutation making them "highly resistant".

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 to date, it said in a statement.

"These preliminary data indicate that oseltamivir resistance in H1N1 viruses is geographically variable but not limited to Europe," it said.

Past studies have found Tamiflu resistance rates ranging from zero percent to 0.5 percent, according to the U.N. agency.

The new "elevated resistance to oseltamivir" appears limited to seasonal H1N1 viruses and does not involve H3N2 or influenza B viruses which are also circulating, the WHO said.

"This means that oseltamivir would most likely be ineffective for treating or preventing infections caused by these resistant H1N1 strains, although the drug will be effective against other influenza virus infections," it added.

Tamiflu has been proposed for prevention and treatment of H5N1 bird flu in humans. Health experts fear the virus, which mainly affects poultry, could mutate into a form easily spread among people which cld spark a deadly pandemic.

UNEXPECTED

The WHO said it was still contacting national health authorities worldwide, but that neither Japan -- where Tamiflu is widely prescribed for ordinary flu -- nor Hong Kong had reported resistance to the antiviral.

A preliminary survey issued by the European Centre for Disease Control (ECDC) this week said that of 148 samples of influenza A virus isolated from 10 European countries during November and December, 19 showed signs of resistance to Tamiflu.

Of 16 samples from Norway, 12 tested positive for resistance against Tamiflu, according to the ECDC study.

"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. (reporting by Stephanie Nebehay, editing by Ralph Boulton) 

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coyote Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: April 25 2007 Location: United States Status: Offline Points: 8395	Post Options Post Reply Quote coyote Report Post Thanks(0) Quote Reply Topic: WHO reports some Tamiflu-resistant flu in U.S. Posted: February 01 2008 at 3:30am
	WHO reports some Tamiflu-resistant flu in U.S. Fri 1 Feb 2008, 11:04 GMT [-] Text [+] GENEVA, Feb 1 (Reuters) - The main influenza virus circulating in the United States has shown raised resistance to Roche Holding Ag's Tamiflu, already found to be less potent in parts of Europe, the World Health Organisation (WHO) said on Friday. The WHO said that until further study was done, it was too early to know what if any potential there might be for such an increase in resistance to Tamiflu to occur in H5N1 bird flu viruses. The agency was not changing its recommendation Tamiflu be used for prevention and treatment of human bird flu. The WHO said it was still investigating the extent of resistance worldwide to Tamiflu, known generically as oseltamivir, in some H1N1 viruses which have a mutation making them "highly resistant". 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 to date, it said in a statement. "These preliminary data indicate that oseltamivir resistance in H1N1 viruses is geographically variable but not limited to Europe," it said. Past studies have found Tamiflu resistance rates ranging from zero percent to 0.5 percent, according to the U.N. agency. The new "elevated resistance to oseltamivir" appears limited to seasonal H1N1 viruses and does not involve H3N2 or influenza B viruses which are also circulating, the WHO said. "This means that oseltamivir would most likely be ineffective for treating or preventing infections caused by these resistant H1N1 strains, although the drug will be effective against other influenza virus infections," it added. Tamiflu has been proposed for prevention and treatment of H5N1 bird flu in humans. Health experts fear the virus, which mainly affects poultry, could mutate into a form easily spread among people which cld spark a deadly pandemic. UNEXPECTED The WHO said it was still contacting national health authorities worldwide, but that neither Japan -- where Tamiflu is widely prescribed for ordinary flu -- nor Hong Kong had reported resistance to the antiviral. A preliminary survey issued by the European Centre for Disease Control (ECDC) this week said that of 148 samples of influenza A virus isolated from 10 European countries during November and December, 19 showed signs of resistance to Tamiflu. Of 16 samples from Norway, 12 tested positive for resistance against Tamiflu, according to the ECDC study. "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. (reporting by Stephanie Nebehay, editing by Ralph Boulton) © Reuters 2008. All Rights Reserved. \| Learn more about Reuters
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