The investigators are to publish their report on Tuesday in the journal Nature and to present some of the details at the Conference on Retroviruses and Opportunistic Infections in Seattle.

Publicly, the scientists are describing the case as a long-term remission. In interviews, most experts are calling it a cure, with the caveat that it is hard to know how to define the word when there are only two known instances.

Both milestones resulted from bone-marrow transplants given to infected patients. But the transplants were intended to treat cancer in the patients, not H.I.V.