Study finds drug-resistant flu virus in Japan
Tue Apr 3, 2007 4:00pm ET
CHICAGO, April 3 (Reuters) - Type B flu viruses, which usually cause smaller epidemics than type A, developed partial resistance to two front-line anti-viral drugs used to combat seasonal influenza, according to a study published on Tuesday.
While there has been evidence of some type A flu viruses developing a resistance to anti-viral drugs, researchers at the University of Tokyo said until their study there has been only limited information involving type B.
The research involved Tamiflu, an antiviral drug made by Roche (ROG.V: Quote, Profile , Research) and Gilead Sciences (GILD.O: Quote, Profile , Research), and Relenza, made by GlaxoSmithKline (GSK.L: Quote, Profile , Research)(GSK.N: Quote, Profile , Research) and Biota Holdings (BTA.AX: Quote, Profile , Research), and known generically as zanamivir.
Tamiflu, also known as oseltamivir, is the first choice against both seasonal flu and the H5N1 avian influenza.
The findings come from Japan where both drugs to prevent and treat seasonal flu are used more extensively than anywhere else in the world. The study involved an influenza B virus outbreak in the winter of 2004-2005 that caused a widespread epidemic.
Writing in this week's journal of the American Medical Association, researchers said they collected flu B virus samples from 74 children before and after Tamiflu use and from 348 influenza patients -- also mostly children -- who were not treated with the drug.
They said they found a virus with reduced drug sensitivity in one of the 74 children who had received Tamiflu. In addition, seven of the 422 influenza B viruses isolated from untreated patients were found to have reduced sensitivity to Relenza, Tamiflu, or both.
Drug resistant flu viruses present a risk because the mutations can make current drugs ineffective for both seasonal flu and a potentially devastating bird flu epidemic.
An editorial in the same issue commenting on the study said it raised more questions than it answered.
But, it said, "some facts are strikingly clear. Influenza B mutants with reduced sensitivity to (anti-viral drugs) are circulating, and these viruses can cause infections with no difference in duration of symptoms...
"Contrary to what had been hoped until now, some resistant variants are vigorous pathogens. Whether these viruses arise by spontaneous mutation ... or whether they are transmitted within families or acquired from the community, the resistant variants may be here to stay," the editorial added. |
