Tamiflu, the most effective weapon for treating the flu, is now almost useless against the most common strain, according to new research from the Centers for Disease Control and Prevention.
“We’ve probably sold more tamiflu this year than we’ve sold in the last several years,” said one pharmacist.

Patients began hoarding it and government agencies, including King County, started stockpiling the drug as a potential treatment for the bird flu. But now comes new research from the CDC that that tamiflu, also known as oseltamivir, is no longer effective even against the most common type of the flu, the A-strain.

Prior to last year, resistance to oseltamivir was detected in less than 1 percent of isolates that were sent in for surveillance. Last year about 12 percent of the influenza A H1N1 viruses were resistant to oseltamivir, and this season it looks like approximately 98 percent, almost 100 percent, of those viruses are resistant to oseltamivir.

Researchers wanted to know if the patients themselves had built up a resistance to the drug. “We found out that none of those patients took oseltamivir before their infection, so their resistance was in no way related to drug use,” said Dr. Alicia m. Fry, M.P.H., U.S. Centers for Disease Control and Prevention.
Tamiflu is still effective against the less common flu, the B-strain. The study appears in this week’s Journal of American Medical Association.