Power Broker

It's for this reason, Fauci concludes, that the best hope for preventing the further spread of AIDS lies in the development of a safe and effective vaccine--a goal that remains stubbornly elusive after 15 years of research. That leaves Fauci with his greatest concern, "the impending catastrophe internationally, which is beyond our imagination." He points to the staggering number of people infected with HIV--36 million around the world, 26 million of them in sub-Saharan Africa alone.

Still, having attended the U.N. AIDS conference in June, Fauci sees reason for hope. "Only recently," he says, "have world leaders recognized the enormity and complexity of the global nature of the AIDS epidemic." That sets the stage, he believes, for a worldwide assault on AIDS. Guess who will be leading the charge.

--Reported by Anne Moffett/Washington