Woman to Man Low Risk

Women are much more likely than men to become infected by an HIV positive heterosexual partner, according to a study released in August, 1997.

Heterosexual Transmission

Announcing the results of the nation's largest study of heterosexual transmission of HIV, researchers at the University of California, San Francisco, found there was a very low rate of infection among heterosexual couples with one HIV positive partner.

Scientists now believe female-to-male transmission is rare. Women were about eight times more likely than men to become infected by their HIV positive partners. The probability of HIV-positive women infecting their male partners with the virus was found to be significantly low.

Risk Factors

We now know many of the risk factors that affect the likelihood of transmission between infected individuals and their heterosexual partners. The risk factors for HIV infection among heterosexuals are unprotected anal receptive sex, lack of condom use, injection drug use, sharing of tainted injection equipment, and the presence of a sexually transmitted disease (STD). Elimination or modification of these factors would result in reduced transmission of HIV.

The UCSF study showed that a history of STDs and injection drug use greatly increased HIV transmission risk from the HIV positive male to his female partner.


Of the 77 HIV positive male injection drug users, 22 percent transmitted the virus to their partners. Of the 163 women who had an STD, 25 percent became infected.

More Info

The results of the UCSF study of heterosexual couples with one HIV infected partner were published in the August '97 issue of the American Journal of Epidemiology.