For just the second time since the global epidemic began, a patient appears to have been cured of infection with H.I.V., the virus that causes AIDS. The news comes nearly 12 years to the day after the first patient known to be cured, a feat that researchers have long tried, and failed, to duplicate. The surprise success now confirms that a cure for H.I.V. infection is possible, if difficult, researchers said.

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.

Dr. Wensing is co-leader of IciStem, a consortium of European scientists studying stem cell transplants to treat H.I.V. infection. The consortium is supported by AMFAR, the American AIDS research organization. The new patient has chosen to remain anonymous, and the scientists referred to him only as the “London patient.”

“I feel a sense of responsibility to help the doctors understand how it happened so they can develop the science,” he told The New York Times in an email. Read more via New York Times