San Francisco Chronicle (SF); Wednesday, September 25, 1991
Charles Petit, Chronicle Science Writer

While many studies in recent years have suggested that the danger of contracting AIDS is higher for women during unprotected sex than for men, the new report is the most complete and its risk ratio is the highest reported in the medical literature.

The report, published in today's issue of the Journal of the American Medical Association, shows that only one of 72 men whose regular female partners were infected by the human immunodeficiency virus caught it. However, 61 of 307 women whose regular sex partner was a man carrying the AIDS virus became infected.

The scientists calculated a "relative risk" that suggests that when it comes to AIDS, unprotected heterosexual intercourse is at least 17 times more dangerous for women than for men.

Nancy Padian, lead author of the study and an assistant professor of epidemiology at the University of California at San Francisco, said she worries that some heterosexual men will interpret the relatively low risk to themselves to mean they can stop using condoms or other safe-sex methods.

NOT A 'GREEN LIGHT'

"My fear is that some men will think this is a green light," said Padian. Even if the risk is lower for men, "you don't shoot craps with something that kills you," she said.

The authors of the study said that the actual risk to women may be considerably higher than what they calculated from their data. The one woman in the study who passed the virus to a partner -- her husband -- was also in a "swinging singles" club.

She and her husband told interviewers that in the previous five years, she had thousands of sexual contacts with hundreds of men which, the report said, may have increased her ability to pass on infections to her husband.

In addition, she and her husband both reported genital bleeding during sex together and told investigators she often had sex with the husband immediately after sex with another man.

Major uncertainties remain, Padian said. The men in the study who were infected by HIV had, on average, more symptoms of AIDS than the women who were positive for the virus. Some studies suggest that as the disease progresses, infectivity goes up. "This could explain part of the different rates of transmission in the couples we studied," she said.

Other AIDS experts agree with Padian's worry over the impact of the report on the behavior of some men.

'BE CAREFUL'

"The risk may be higher for women, but it may not be different enough to affect what we say to people, which is to be careful," said Dr. Thomas Peterman, a medical epidemiologist at the national Centers for Disease Control in Atlanta.

Several years ago, Peterman studied partners of people who got AIDS from transfusions. In that study, two of 25 infected women passed the virus to their male partners, while 10 of 55 infected men passed it to their female partners.

AIDS workers say that although the numbers are small, more and more cases of HIV infection and AIDS are appearing among men and women whose only risk factor has been unprotected sex.

"In the past year I have had five men come in who got the disease from their female partners, and all were shocked," said Catherine Maier, coordinator of women's and children's services for the San Francisco AIDS Foundation.

AFRICAN PARADOX

In Africa, many researchers have noted, the disease is largely passed heterosexually, with high rates of infection in both men and women. The higher apparent risk for women than men in the United States seems out of line with the pattern of the disease in Africa. "It is a paradox we don't understand very well," said Andrew Moss, chief of medicine and epidemiology at San Francisco General Hospital.

In the United States by contrast, the infection continues to be passed primarily by sex among gay men and by sharing of drug needles. In American men, only 3.1 percent of cases of AIDS were acquired by sex with women, while among women, 34.8 percent got it via sex with men.

Always watch for outdated information. This article first appeared in 1991. This material is designed to support, not replace, the relationship that exists between you and your doctor.

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