In November, a potential breakthrough was reported in the fight against AIDS. Doctors of a man who suffered from AIDS said he appeared to have been cured of the disease 20 months after receiving a targeted bone marrow transplant normally used to fight leukemia. Dr. Gero Huetter said his 42-year-old patient, an American living in Berlin who was not identified, had been infected with the AIDS virus for more than a decade. But after undergoing a transplant of genetically selected bone marrow, he no longer shows signs of carrying the virus. While researchers, and the doctors themselves, caution that the case might be no more than a fluke, others say it may inspire a greater interest in gene therapy to fight the disease that claims 2 million lives each year. The virus has infected 33 million people worldwide.