Six women in San Francisco have developed AIDS through sexual contact with men, health officials said. “We’re in the midst of a fatal transmissible disease in San Francisco, and it’s up to everyone to understand the true risks involved,” Dr. Dean Echenberg, chief of communicable disease control, said in releasing the city’s AIDS report for May. “The lesson that everyone must learn is that AIDS is above all a sexually transmitted disease,” Echenberg said. “It is not limited to homosexual and bisexual men, and it is not limited to men or women who have multiple sexual partners.” The May figures showed 83 new cases and 61 deaths. Since the epidemic first was noted in 1981, 2,042 AIDS cases have been diagnosed in the city, 1,155 of them resulting in death.