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, has been found with varying frequency in various areas of four European countries, Canada and the United States.
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