The drug works by preventing the virus from making more virus in the body, Garcia-Martinez said.
"The biggest caveat is that even though we're using humanized mice, this is not a human being," he said. On the other hand, studies in humans should let researchers know soon if it works in people, and the mice research helps scientists "get a handle on what the virus will do in humans," he said.
So why not give Truvada to everyone at risk for HIV infection, such as people who have many sex partners?
For one thing, the drug is expensive, costing hundreds of dollars a month. And there's concern that people would take more sexual risks if they were to take the drug, potentially robbing the medication of its infection-preventing power if it's not 100 percent effective.
Side effects could be a problem too, as could forgetting to take the drug.
Even so, the idea of a preventive drug treatment -- a "chemical condom," as some call it -- might not be out of the question.
"It's reasonable to think that this might one day prove to be a strategy you could use," said A. David Paltiel, a professor who studies HIV issues at the Yale School of Medicine.
The AIDS InfoNet has more on Truvada.
SOURCES: J. Victor Garcia-Martinez, Ph.D., professor, medicine, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, N.C.; A. David Paltiel, Ph.D., professor, public health, and acting head, division of health policy and administration, Yale School of Medicine, New Haven, Conn.; Jan. 21, 2010, PloS One, online
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