Since new broke this week that a second HIV-positive patient was cured of the virus that causes AIDS, four people asked Dr. Ray Martins if they could have the stem-cell surgery.

The Washington doctor said he wouldn't recommend it.

A scientific team from several UK universities reported details of the case in Seattle, describing it as "long-term remission", although they added that "it is too early to say with certainty that he has been cured of HIV".

However doctors are hailing news of a potential breakthrough on a condition that has killed hundreds of thousands in the United States alone. But the operation is so onerous and HIV now so manageable - that it could be a classic case of the cure being worse than the disease.

HIV was once a death sentence - it has killed some 35 million people worldwide. But now, by taking one or two pills a day, most patients can suppress viral loads to the point that they can neither be detected nor passed on to others.

The still-experimental surgery involves chemotherapy and a bone marrow transplant using stem cells. It's painful, risky, and threatens harsh side effects that can last for years.

"It's so dangerous, " Martins said. "I wouldn't do that to someone who is healthy with HIV."

Steven Deeks, a University of California, San Francisco professor involved in the cure research, said the procedure should be used only on cancer patients with HIV.

"This approach is just too, too dangerous for the treatment of HIV by itself," Deeks said.

The London man who was reported to be cured of HIV this week and the Berlin patient, who was cured in 2007, both had cancer.

A third man from Dusseldorf, Germany, has had a similar transplant and been off his HIV medication for more than three months, Deeks said. But doctors want more time before declaring him cured.

Deeks said more research is needed before the treatment can be made available to the broader population infected with HIV.

"The big question is how do we use the lessons learned from theses cases to come up with something that is safer and more scalable," he said. "That's an area of intense research. "