Swine Flu Variation Emerges With Power to Resist Drug Treatment

June 9 (Bloomberg) -- A novel form of the swine flu virus that swept the globe in 2009 has emerged in Australia and Singapore, carrying a genetic twist that helps it resist Roche Holding AG’s Tamiflu and GlaxoSmithKline Plc’s Relenza, researchers said.

More than 10 percent of the infections in Singapore and 30 percent of those in northern Australia tested in early 2011 had mildly reduced sensitivity to the two drugs that are the mainstay of influenza treatment, according to a report today from the World Health Organization’s influenza research group in North Melbourne, Australia. BioCryst Pharmaceuticals Inc.’s experimental flu drug peramivir remained an effective treatment against the virus in laboratory tests, the researchers said.

The new variation of H1N1 mixed with an older form of the virus in at least one patient, the researchers said. The infection was extremely resistant to Tamiflu and the individual, who had a weakened immune system, died of multiple organ failure. With other flu strains circulating in the U.K. and elsewhere, there is a risk of future combinations of drug-resistant virus, they said.

The new variation appears to spread easily among people, according to the report in the journal Eurosurveillance. If it circulates widely, researchers said they are concerned that other mutations may occur and trigger even greater drug resistance and more serious illness.

Influenza is a rapidly evolving virus, and the severity of the season depends on which strains are circulating and how well a population has been inoculated. Annual deaths in the U.S. associated with seasonal flu ranged from 3,349 to 48,614 from 1976 to 2007, according to the Centers for Disease Control and Prevention. About 90 percent of flu-related deaths are in people ages 65 or older.

The H1N1 virus was reported in more than 214 countries and caused about 18,450 deaths worldwide through August when the World Health Organization declared an end to the pandemic.

To contact the reporter on this story: Michelle Fay Cortez in Minneapolis at mcortez@bloomberg.net

To contact the editor responsible for this story: Reg Gale at rgale5@bloomberg.net