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The CDC has learned of at least 118 cases of transmission between heterosexual partners. Most heterosexual transmission seen to date has been from men to women, rather than from women to men, suggesting the possibility that women may be less efficient transmitters of the infection. However, at least 14 men have been infected by women, according to Mathilde Krim, a research biologist at the Memorial Sloan-Kettering Cancer Center in Manhattan, and health authorities are concerned about the possible role of prostitutes in spreading the epidemic. Curran thinks it may prove significant that "about 15% of the men whose cases remain unexplained have a history of sexual contact with prostitutes." The U.S. Army is also concerned about this risk, according to Dr. Robert Redfield of Walter Reed Army Medical Center. Soldiers, he says, "are largely in the 18-to-30 age group, a time of being most sexually active."
AIDS appears to be almost entirely a heterosexual disease in the central African countries of Zaïre, Rwanda and Burundi, where it affects women and men in equal numbers. According to a Canadian researcher working in East Africa, "Prostitution seems to have played a key role in African AIDS." Many of the affected males, he notes, are "heterosexuals who have a large number of sexual partners." Virologist Myron Essex of the Harvard school of public health thinks that as many as one out of every 20 people is infected (though not necessarily ill) in Africa's "AIDS belt," which also includes parts of Kenya, Uganda and Tanzania. Some researchers see this as "a foretaste" of what will occur in the U.S., but many disagree. They point to Third World conditions that may promote the disease. Among them: the presence of feces in drinking water, the use and reuse of unsterilized needles in many small clinics and, possibly, even local rituals that involve scarification and the exchange of blood.
Squalid conditions, poverty and a semitropical environment may also play a role in the high rate of AIDS in Haiti and, oddly enough, in parts of southeastern Florida. Belle Glade (pop. 19,000), Fla., with 46 cases, has the highest incidence in the U.S. "There is raw sewage on the ground and rats running all around," says Dr. Mark Whiteside of Miami's Tropical Medicine Clinic. Filth, insects and a high rate of tuberculosis, he suggests, might contribute to the epidemic.
The prevalence of the AIDS virus in central Africa has led researchers to speculate that the disease originated on that continent. Harvard's Essex believes the scourge got its start in monkeys, specifically the African green monkey. In sampling the blood of 200 greens from this region, Essex found that 70% of them were infected with a virus similar to the one that causes AIDS in humans. Curiously, the virus does not seem to harm the monkeys, a fact that might hold important clues for future research. Essex suspects that in the past 20 to 40 years, the virus spread from monkeys to man. Other viruses have made this leap--notably jungle yellow fever virus--and, he notes, the greens often live in close association with people and frequently bite them. How the disease might have traveled from Africa to the U.S. and Haiti is anybody's guess. One "intriguing" clue, says Dr. Peter Piot of the Institute for Tropical Medicine in Antwerp, Belgium, is that several thousand Haitians lived in Kinshasa, Zaïre, from the early 1960s to the mid-'70s, and most of them, he says, have since moved to North America and Europe. As another researcher put it, the virus "didn't just fall out of the sky."
There has so far been just one remark able success in the otherwise losing battle to contain the spread of AIDS. That is the rapid development of tests to detect signs of the virus in donor blood. About 2% of AIDS cases in the U.S. have occurred as a result of the contamination of blood used in transfusions or in blood products like the clotting factor needed by hemophiliacs. The toll includes infants, children, even a 66-year-old nun.
See pictures of Africa's AIDS crisis.