UC Berkeley Study Finds AIDS Risk of Heterosexuals to Be Low

A UC Berkeley study of AIDS-infected men and their female sex partners indicated Thursday that the virus is far less infectious to heterosexuals than thought, suggesting a heterosexual AIDS epidemic in the United States is not imminent.

But the Berkeley public health authorities cautioned that heterosexuals can still catch the AIDS virus and that their risk increases with repeated sexual exposure to an infected person and through high-risk sex practices.

“The probabilities are low, but it’s still Russian roulette,” said Nancy Padian, who directed the study, published in today’s Journal of the American Medical Assn.

“The fact that the infectivity of this virus to heterosexuals is low has to be tempered by (the fact that) this is a lethal disease for which there is no cure,” she added.

‘Can Stem This Disease’

“This is very encouraging because it means we can stem this disease if we begin now to institute reasonable behavior modification to reduce the chances of spreading the virus,” said Dr. Warren Winkelstein, another Berkeley researcher.

In the UC Berkeley study, Padian and her colleagues sought to determine the risk of infection to women sexually exposed to men carrying the AIDS virus. Although heterosexual infection has been well documented, there is substantial disagreement about how easy it is to catch the virus.

The researchers studied 97 women who had had sexual relations with 93 AIDS-infected men in the year before the men’s infections were detected.

They found that only repeated sexual contacts with the infected man and the practice of anal intercourse increased the chances of acquiring infection.

31% Become Infected

Of 65 women who had had more than 100 sexual encounters with their infected mate, only 20, or 31%, had themselves become infected.

“Indeed, while this is evidence that male-to-female transmission occurs, what remains striking is how many people do not become infected,” Padian said. “This is a hard disease to transmit.”

Having multiple sex partners, a well-known risk for homosexual men, did not increase the chance of a woman’s becoming infected, the study found, probably because the pool of infected individuals is low, Padian said.

The risk of males contracting acquired immune deficiency syndrome from females was not addressed in the study, but most health experts believe that such risk is probably lower than for women.

Padian said these facts should not detract from the public health message that sexually active people must be selective about their partners, practice monogamy whenever possible and use condoms when the partner’s infection status is not known.

Cases as of Aug. 10

As of Aug. 10, 40,051 cases of AIDS and 23,165 deaths had been reported to the federal Centers for Disease Control. Of those, 1,532 cases, or 4%, were classified as being heterosexually transmitted.

The report done at the University of California, Berkeley was tempered by another study in the same issue of the medical journal that found homosexuals from areas where AIDS cases are rare are continuing to engage in high-risk sex, and that many of them are now becoming infected with the AIDS virus.

Dr. David Fleming, then with the Centers for Disease Control in Atlanta, reported that blood tests of 112 homosexual and bisexual men in New Mexico found that one in seven is now infected with the virus that causes AIDS--similar to the infection rate found in San Francisco in the early 1980s.