Bird flu resistant to anti-viral drug

December 22, 2005

In an article in the December 2005 issue of the New England Journal of Medicine (NEJM), researchers from Oxford University report that two recent avian flu fatalities in Vietnam were patients who had been treated with the anti-viral medication Tamiflu. There has been one other reported case of Tamiflu-resistance in Vietnam.

The NEJM report documents that during treatment of H5N1-infected patients with Tamiflu there can be selection for mutant virus variants that are Tamiflu-resistant. This is also been observed with other more common flu virus types. The chances of Tamiflu-resistance arising during H5N1 infections might be enhanced by two properties of H5N1; its ability to replicate rapidly and its ability to infect the gastrointestinal tract. In such cases, higher doses of Tamiflu and longer course of treatment may be needed. Combination treatment with other anti-viral drugs is a common strategy for dealing with viruses that become drug resistant.