Heterosexuals and AIDS: mixed messages; recently reported studies on heterosexual transmission of AIDS expose some disturbing threats to public health

Science News, July 25, 1987 by Diane D. Edwards

Heterosexuals and AIDS: Mixed Messages

After the first recognized case of AIDSwas described in the United States in 1981, the fatal disease appeared to attack only homosexuals and a few other isolated groups, a situation often perceived as a brutal yet limited medical menace. Now the recognition of heterosexual transmission brings AIDS closer to everyone's home.

Of the nearly 37,000 AIDS cases reportedin the United States as of July 1, approximately 4 percent were classified as heterosexual cases, where the only known source of the AIDS virus was sexual relations with an infected person of the opposite sex. Although relatively few in number, these cases represent the fastest growing group of U.S. patients with AIDS. Elsewhere, percentages of heterosexual cases vary from country to country, but are viewed with equal alarm by world health officials. The World Health Organization estimates that 50 million to 100 million of the world's population will be infected within five years, an unpredictable number of those through heterosexual contacts.

With an increasing proportion of thosedying from AIDS falling outside the originally defined high-risk groups, scientists and health officials are trying to define the boundaries of an AIDS-inflicted future. As part of that effort, studies on heterosexual transmission presented at last month's Third International Conference on AIDS in Washington, D.C., addressed the following questions: What are the factors influencing the heterosexual route to AIDS? Which groups are most likely to be affected? And, perhaps most important, how can the heterosexual spread of the disease be reduced or stopped?

The answers, far from complete andfrequently contradictory, are both hopeful and horrific.

Among the many reports at the meetingwere three that illustrate major areas in AIDS research: the respective roles of sexual promiscuity and intravenous drug use; the prevalence, or extent, of heterosexual transmission; and AIDS among women.

Scientists from the University of Californiaat San Francisco (UCSF) presented data from an ongoing study of 513 heterosexually active women aged 18 years or older, abut 100 of whom are prostitutes. They conclude that it is not the number of sexual partners a woman has, but the "character' of those partners, that determines the woman's risk of developing AIDS. The women, randomly recruited from throughout the city, were enrolled in the study if, in the previous three years, they had had sexual relations with a man known to be infected with the AIDS virus, with a man in a high-risk group (bisexual, intravenous drug user or hemophiliac) or with at least five male sex partners lacking high-risk factors. With 75 percent of the women white, the study is not truly representative of the AIDS situation in the United States, since AIDS is more common among black and Hispanic women, UCSF researcher Judith Cohen told SCIENCE NEWS. It does, however, say something about increased risks among women in general.

When the study began in 1985, none ofthe women tested positive for the presence of blood antibodies against the AIDS virus; by the beginning of 1987, 28 had "seroconverted' and developed antibodies, indicating infection. On the basis of periodic interviews with the women, the scientists conclude that either intravenous drug use or sex with an intravenous drug user will at least double the risk of being infected. Having an infected sexual partner carries a bigger risk, increasing the chances of infection more than three-fold. But having multiple sex partners from no known risk group--whether five or more than 50 over a three-year period--does not make a woman more likely to become infected than a woman who is not "sexually adventurous,' says Cohen.

A survey of more than 500 prostitutesin Nairobi, Kenya, by that country's department of health and the Institute of Tropical Medicine in Antwerp, Belgium, found that the prevalence of seropositives among the prostitute population increased steadily from 8 percent in 1981 to greater than 85 percent in 1987. One postulated factor is the frequent presence of other sexually transmitted diseases, which are thought to make a person more susceptible to AIDS infection. In the Antwerp study, more than 80 percent of the seropositive individuals had other venereal diseases as a predominant risk factor.

Although the researchers admit thisstrong relationship may not hold in a broader population, several other studies presented at the meeting also found a strong correlation between increased risk of infection with the AIDS virus and concurrent venereal disease--particularly genital ulcers. The findings suggest that control of conventional sexual diseases could reduce the spread of AIDS in the heterosexual population.

The study also is tied to one of the keyepidemiologic questions regarding heterosexual transmission: Why does it occur with such relative ease in Africa, where it has always been the primary mode of infection? At least as many women as men there reportedly develop the disease, in sharp contrast to other areas of the world. While researchers try to separate the cultural causes from the scientific factors, African prostitutes-- now considered a major reservoir of the AIDS virus--are the target of intense epidemiologic studies and educational programs.