FRIDAY FEB 1, 2008 (Foodconsumer.org) -- A mutation found in a small percentage of the common influenza virus causing illness this winter in Europe, Canada and the United States makes the virus resistant to the anti-influenza drug Tamiflu, The New York Times cited the World Health Organization as saying Wednesday.
The predominant influenza virus strain found in the winter is influenza A/H1N1 and the Tamiflu-resistant form of the virus is known as influenza A (H1N1 H274Y). The rate of the mutant varies among four European countries, Canada and the US.
In Norway, epidemiologists found the mutation was present in 12 of 16, or 75 percent, of viruses isolated from Norwegian patients in the earliest part of the influenza season, in November and December. This rate was highest among the four European countries - Britain, Denmark, France and Norway.
Overall, a survey of the mutation in 10 European countries by the European Center for Disease Prevention and Control showed the rate was 13 percent. When Norway was excluded, the rate was 5 percent.
In the United States, the Tamiflu resistant strain was found in 9 of 237 or 3.8 percent of patients who suffered either type A or type B in the winter. But because all 9 mutants were in the A(H1N1) category the rate was 6.7 percent among A/H1N1 viruses, Dr Fry said in a telephone interview with the New York Times.
According to the New York Times, scientists were surprised by the finding that the A/H1N1 mutant was on the rise as they used to believe that mutations of this type would make the virus less potent and less likely to spread among people.
Health officials from the WHO and the US were cited by the times as saying that no immediate measures would be taken to change the use of Tamiflu or oseltamivir because the incidence of the mutant virus is still small although WHO officials said they were troubled by the findings.
Tamiflu is a drug that is used in the early stages of influenza to relieve its symptoms and patients treated with the antiviral drug could shorten the suffering period by one or two days. The drug is stockpiled by many countries in a bid to prevent a future influenza pandemic.
Officials downplayed the significance of the findings. "Clearly, this is of global concern, but it is not a global problem now," Dr. Frederick G. Hayden, an influenza expert at the WHO, said in a telephone interview.
Scientists at the U.S. Centers for Disease Control and Prevention in Atlanta said the standard influenza vaccine still protects against the mutant virus.
It's unknown what caused the mutation. But use of Tamiflu may not be the cause. Tamiflu is most commonly used in Japan, but the country is low in the incidence of the mutant influenza viruses. On the contrast, Norway has the highest rate of the mutation although in the country doctors do not use Tamiflu to treat influenza, according to time.com.
Healthy people do not need any vaccine or antiviral drug to treat common influenza because the immune system has the capability to overcome the illness, a foodconsumer.org scientist suggested.