# 1593
The news has been filtering out for about a week. A disturbingly high number of Tamiflu resistant influenza samples have been detected, first in Europe, and now in the United States and Canada.
Two years ago, Amantadine and Rimantandin, both older antivirals, were rendered largely useless against seasonal flu by a sudden upsurge in resistant viruses. Over the course of 2 years, resistant strains went from the single digits, to over 90% of samples tested.
While the number of Tamiflu (oseltamivir) resistant strains is still low, scientists are worried that one of our few weapons against viral influenza may be starting to lose its effectiveness against seasonal flu.
More data is required before we can know if this is a trend, or an anomaly. For now, Tamiflu appears to remain effective against a majority of the influenza A and B strains currently in circulation.
WHO reports Tamiflu-resistant flu in U.S. and Canada
GENEVA (Reuters) - The main flu virus circulating in the United States and Canada has shown "elevated resistance" to the antiviral drug Tamiflu, in line with findings in parts of Europe, the World Health Organisation (WHO) said on Friday.
The United Nations agency said it was too early to know what potential there may be for increased Tamiflu resistance in H5N1 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 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 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. In Canada, 8 out of 81 samples showed resistance -- more than a 10 percent resistance rate, WHO spokeswoman Sari Setiogi said.
"These preliminary data indicate that oseltamivir resistance in H1N1 viruses is geographically variable but not limited to Europe," the WHO said in a statement.
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 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.
