The World Health Organization (W.H.O.) announced on Wednesday, January 30, 2008, that a small but significant percentage of the cases of influenza in four European countries, Canada, and the U.S. this year have proven to be resistant to the anti-influenza drug Tamiflu.
Mutant Strain of Influenza Found: Tamiflu ineffective against this drug-resistant form of flu virus
Scientists have expressed surprise at finding a drug-resistant mutant strain of influenza because they had believed that mutations of this kind would actually be less potent and less likely to spread.
Tamiflu, also known as oseltamivir, is one of the antiviral drugs used to treat influenza. It must be started within the first 48 hours after symptoms first appear. It has been ineffective in the small number of cases in which the virus has mutated; otherwise if taken in time, Tamiflu continues to reduce the duration and severity of flu symptoms and helps to prevent complications such as pneumonia.
The standard tamiflu vaccine given this year, however is effective against this mutant strain according to epidemiologists at the Centers for Disease Control and Prevention (CDC) in Atlanta, GA. The predominant strain of influenza this year is influenza A(H1N1) and the mutant strain is known as influenza A(H1N1 H274Y). However in the U.S. Influenza B has also been found this year.
Mutant Strain of Influenza Found:
Norwegian epidemiologists first called attention to this problem last week. The Norwegian mutation rate (75%) was the highest among the European countries which have reported finding this mutation. The other countries reporting the mutant strain are Britain, France and Denmark. Overall, the European Centers for Disease Control and Prevention found a 13% mutation rate in the ten countries it monitors.
In the U.S. so far this year, the Tamiflu-resistant form of tamiflu has been found in 6.7% of the cases studied. All of them were of the influenza A(H1N1) variety. Exact figures for Canada were not available, but officials at W.H.O. have expressed concern for the global implications of this mutation.
According to W.H.O. officials, data has been collected and experts around the world have agreed to continue to study this problem and collect data. It is hoped that a larger number of patients can be studied to better determine the virulence of this strain. Experts also want to study the frequency of this mutation as well as patterns of transmission and distribution throughout the world. W.H.O. is a United Nations agency based in Geneva, Switzerland.
An overuse of Tamiflu is not suspected to be the cause of this mutation due to the fact that no cases of the mutant strain have been found in Japan where the drug is used widely. There are no plans at the present time to change the way Tamiflu is being used because the incidence of this mutation is still small.
Practicing good handwashing and avoiding crowds are among the most effective ways to avoid colds and flu.