Patients with AIDS may need to start mixing stronger drug cocktails.

A recent study led by Joseph J. Eron, associate professor of medicine, showed that even with the best drug therapy, drug-resistant strains of HIV can still be detected in semen and potentially passed on to others.

This means that even while patients are taking drugs, those traces of the virus still in the body may multiply and mutate to new forms uncontrollable by drugs.

The study focused on 11 HIV-infected men in North Carolina and Switzerland, five of whom had not previously taken drugs for the disease. All 11 patients were given a variety of antiviral AIDS drugs and were followed for an average of 58 weeks.

At the beginning of the study, three of the six patients who had taken drugs prior to the study showed strains of drug-resistant HIV in their semen and continued to do so throughout treatment. Further, eight out of 10 patients developed "new resistance mutations" in their blood or semen (or both).

"This study has definite public health implications," Eron says. "If we can't adequately suppress the virus to undetectable levels, then it is likely that drug-resistant strains of HIV can be shed in genital secretions. And that's virus available for transmission."

Eron suggests that scientists need to learn more about the drugs they use and whether or not the drugs can reach the genital tract at levels high enough to suppress the virus.