A report at the weekend from the European Center for Disease Prevention and Control found that 19 out of 148, or about 13 percent, of influenza viruses tested "showed evidence of resistance to oseltamivir," the drug marketed in the United States by Nutley, N.J.-based Hoffmann-La Roche Inc. as Tamiflu.

The samples, tested by the EU-funded VIRGIL network, were isolated in 10 European nations during November and December last year.

The majority of the samples showing resistance came from Norway, where 12 of 16 samples isolated showed evidence that they were resistant to the drug.

In a statement, the center said it was "impossible to say what the level of resistance (to Tamiflu) is in influenza across Europe," but added "the proportion of influenza viruses exhibiting resistance … must be significant, but not as high as in Norway."

It said experts from the center, the European Commission and the World Health Organization were currently assessing the data and would shortly publish an assessment.

Roche spokesman Terence Hurley told United Press International more research was needed, but noted that the strains tested in Europe were normal seasonal flu viruses, not the pandemic strains for which Tamiflu is stockpiled in the United States.

"More extensive surveillance globally is required to establish the relative prevalence and geographical distribution of this (strain) of Tamiflu-resistant viruses and to evaluate their potential impact on the effectiveness of drug use," he said.

"It's also important to note that data from the United States indicates a very low rate of oseltamivir resistance among the influenza strains currently circulating" there, he added.

In November 2005 President Bush allocated $1.4 billion to build U.S. stockpiles of anti-viral drugs such as Tamiflu in case of a pandemic.

--

Shaun Waterman, UPI Homeland and National Security Editor