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."