Another expert said some of the increasing resistance has less to do with Tamiflu and more to do with the natural evolution of viruses.
"It's not the same as the analogy to bacteria that have developed resistance when they get more virulent," explained Dr. Len Horovitz, a pulmonary specialist with Lenox Hill Hospital in New York City. "These are natural mutational shifts and drifts, not a result of the overuse of [Tamiflu]. Just because it's becoming more resistant does not mean that it's a more deadly virus."
A second study has found that the Tamiflu-resistant virus still poses a significant health threat to certain groups of patients, in particular those with compromised immune systems who are hospitalized.
Both studies were expected to be published in the March 11 issue of the Journal of the American Medical Association, but were released Monday.
In light of the increased resistance to Tamiflu, the CDC in December recommended that doctors test suspected flu cases to determine the exact strain of the virus and what medications should be prescribed based on results of these tests.
In 2006, the CDC issued a recommendation against using two other flu drugs, amantadine and rimantadine, owing to resistant strains of influenza B and H3. Those drugs work by a different mechanism than Tamiflu and the other drug in its class, Relenza (zanamivir).
The second study, from researchers in the Netherlands, recommended that patients be tested for specific strains of influenza and, if needed, be isolated so as to avoid hospital outbreaks.
But, the authors also cautioned, the conclusions and recommendations were based on only a small number of patients.
A third study, this one published in the March 4 issue of JAMA, found that the flu shot was more effective in reducing influenza- and pneumonia-related health-care visits than the nasal spray form of the vaccine. Pneumonia is a potentially f
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