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<em>Science Translational Medicine</em>: Genital Samples Reveal HIV Transmission Risk

A small sample of genital secretions from a heterosexual person with HIV can reveal the odds of that person transmitting the disease to a partner, reports a new study in the 6 April issue of Science Translational Medicine.

“Our study is the first to show that the quantity of HIV in a genital sample predicts the risk of HIV transmission. The results add tremendous weight to 20 years of genital HIV research,” said lead author Jared Baeten, assistant professor of global health at the University of Washington in Seattle.

Looking at HIV levels in genital samples could be a new way to test the potential benefits of up-and-coming HIV prevention strategies like microbicides and antiretroviral medications.

The mammoth study in seven African countries (Botswana, Kenya, Rwanda, South Africa, Tanzania, Uganda and Zambia) followed 2,500 heterosexual couples in which one partner had HIV and the other did not.

More couples had a female partner carrying the virus than a male partner. For two years, Beaten and colleagues checked in with the couples every three months while also providing HIV testing, counseling, and prevention services.

Listen to an informal conversation with Jared Baeten or download the MP3.

During the study, HIV transmission occurred between partners in 78 couples. The research team measured HIV levels in the genital samples of those individuals who transmitted HIV to their partners, and compared the samples to HIV levels in individuals who did not transmit HIV.

This involved taking a soft swab from the cervix of HIV infected women and a semen sample from HIV infected men. The researchers found that the higher the amount of HIV in a genital sample, the greater the risk for transmission of the virus between partners.

“Importantly, we found that genital HIV concentrations predicted HIV transmission risk independent of levels of HIV in the blood,” Baeten said.

The results validate 20 years of research and many dozens of studies that have looked at genital HIV levels as a potential measure of HIV infectiousness. Thus, future studies will be able to measure genital HIV levels with confidence that such levels do in fact indicate transmission risk.


Read the report, “Genital HIV-1 RNA Levels Predict Risk of Heterosexual HIV-1 Transmission,” by Jared Baeten et al.

Listen to an informal conversation with Jared Baeten.

Visit Science Translational Medicine.