WEDNESDAY, Nov. 7, 2001 (HealthDayNews) -- The assumption seems logical: As the amount of the AIDS virus in a person's blood rises, his or her ability to infect others would grow at the same rate. But little about AIDS is simple, and new research in Africa suggests this equation isn't quite true, especially for women.
Something about the biology of HIV-positive women makes them much more contagious than the level of virus in their blood would suggest. Though the finding doesn't necessarily mean that sex with an infected woman is more dangerous than sex with an infected man, it does point to the importance of not treating both genders the same way, one expert says.
"It's another step on the road to understanding the physiology that drives sexual transmission," says Kevin Ryan, a microbiologist with the AIDS division of the National Institute of Allergy and Infectious Diseases. "This points us in a productive direction, but we're not at the end of the road of understanding what's going on."
Researchers from the University of Alabama at Birmingham surveyed 1,022 heterosexual couples in Lusaka, Zambia, a country in south-central Africa, where more than 80 percent of all HIV cases in the world occur. HIV is the virus that causes AIDS.
In all the couples, one person was infected with HIV. The purpose of the study was to investigate the link between "viral loads," the levels of virus in the blood and the rates of infection among the couples.
"We know that some people are more contagious than others, and some are more vulnerable to others," says study co-author Dr. Susan Allen, professor of epidemiology and international health at the University of Alabama.
The study is described in the October issue of the medical journal AIDS Research and Human Retroviruses.
Women with high viral loads were seven times more likely than other infected women to transmit the disease, Allen says. Men with high viral loads were only twice as likely as other infected men to spread HIV.
Researchers had assumed that it's easier to transmit the virus from men to women, from semen to the vagina, instead of the other way around, from vaginal fluids into a penis. Allen says, "But ours is the third study to show that for some reason, that doesn't seem to be the case."
Allen says the research provides information that could be used to develop partial AIDS vaccines for Africans, who are unable to afford the expensive drugs now commonly used in the United States to keep AIDS at bay. Development of complete vaccines that would block the AIDS virus entirely are far off, but partial vaccines that would shrink viral loads do appear likely in the near future, she says.
"The impact on transmission from people who are being treated is going to be much more dramatic in women than in men."
Ryan says the research may also help doctors properly adjust the combinations of medicines known as "cocktails" that have revolutionized AIDS treatment.
"We have a very good idea of what they do for the patient, but we have less understanding of what they do for the person's infectiousness," he says.
What To Do
Time Magazine recently explored the devastation that AIDS has unleashed on Africa.
Learn the basics of HIV, including how it can be transmitted, in these fact sheets from the Gay Men's Health Crisis.
