By Jason Gale
Feb. 1 (Bloomberg) -- Influenza strains resistant to Roche Holding AG's Tamiflu were found in a samples from five more countries, indicating the mutant bug is more widespread than health officials reported earlier this week.
Tests on 437 virus specimens from patients with the H1N1 flu strain in 18 countries found 59 that harbored resistance to the pill, the European Centre for Disease Prevention and Control said in a statement yesterday. Resistant viruses were found in nine European countries, with Norway accounting for almost half.
Emerging resistance to Tamiflu, also known as oseltamivir, has led doctors to consider GlaxoSmithKline Plc's Relenza and other treatments for a disease the World Health Organization estimates causes 250,000 to 500,000 deaths globally each year. Experts are assessing the significance of the data and will release an interim assessment in the coming days, ECDC said.
``At this stage, it is impossible to say what the level of resistance is in influenza across Europe,'' the Stockholm-based health agency said. ``However from the limited data, the proportion of influenza viruses exhibiting resistance to oseltamivir must be significant, but not as high as in Norway.''
The H1N1 viruses identified in Europe that aren't susceptible to Tamiflu carry a so-called H274Y gene mutation that confers ``high-level resistance,'' Frederick Hayden, a researcher with the WHO's Global Influenza Program in Geneva, said in a Jan. 28 interview.
Of 109 H1N1 viral samples tested in the U.S. during the 2007-2008 flu season, 5.5 showed the same resistance-inducing mutation, according to the Centers for Disease Control and Prevention in Atlanta.
Recent tests on samples from Europe found viruses with the H274Y mutation in Germany, Netherlands, Portugal, Sweden and Finland, scientists from the U.K.'s Health Protection Agency said in a report published yesterday in Eurosurveillance, a newsletter on communicable diseases.
Earlier sampling found the mutant strain in France, the U.K., Denmark, France and Norway, the ECDC said in a Jan. 27 risk assessment report. Of 37 samples from Norway tested, 26 harbor resistance, the agency said yesterday.
``The oseltamivir resistance investigation is still in its early stages,'' researchers from the ECDC's Influenza Project Team wrote in a separate report in yesterday's Eurosurveillance. ``A more accurate picture will only emerge when many more specimens have been tested and more epidemiological information is available.''
Tests so far show that the mutated viruses are susceptible to Relenza and an older class of antiviral drugs known as adamantanes, the researchers said. There's insufficient evidence for authorities to consider changes to clinical guidelines, the researchers said.
No More Virulent
People who become ill with the Tamiflu-resistant H1N1 strain don't appear to become any more sick than people infected with ``normal'' seasonal flu, ECDC said.
Tamiflu, which generated 2.09 billion francs ($1.9 billion) in sales for Basel, Switzerland-based Roche in 2007, is the company's fifth-best-selling drug. Relenza, an inhaled medicine, had sales of 91 million pounds ($181 million) in 2006 for London-based Glaxo.
The medicines are being stockpiled by the Geneva-based WHO and governments around the world for use in the event of a pandemic, and to treat the H5N1 avian flu strain that's spread to more than 60 countries, infecting people in 14 of them.
The H5N1 bird flu strain could trigger a global outbreak if it adopts some of the characteristics of seasonal flu that enable it to be spread easily through coughing and sneezing.
To contact the reporter on this story: Jason Gale in Singapore atLast Updated: February 1, 2008 00:53 EST