Mutant Flu Virus Is Found That Resists Popular Drug

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A small but significant percentage of the main influenza virus causing illness this winter in Europe, Canada and the United States has a mutation that makes it resistant to the anti-influenza drug Tamiflu, the World Health Organization said Wednesday.

Scientists said they were surprised by the finding because they had believed that mutations of this type generally made the virus less potent and less easily spread among people. The predominant influenza virus circulating this winter is influenza A/H1N1. The Tamiflu-resistant form of the virus, known as influenza A(H1N1 H274Y), has been found with varying frequency in various areas of four European countries, Canada and the United States.

There are no immediate plans to recommend changes in the use of Tamiflu, which is also known as oseltamivir, officials from the W.H.O. and the United States said in interviews, because the incidence of the mutant virus is still small. Tamiflu is one of the antiviral drugs used to treat influenza in its early stages.

Nevertheless, officials from the W.H.O., a United Nations agency in Geneva, said they were troubled by the discovery.

“Clearly, this is of global concern, but it is not a global problem now,” Dr. Frederick G. Hayden, an influenza expert at the organization, said in a telephone interview.

NY Times