Even on successful antiretroviral (ARV) therapy, about 16 percent of women and 4 percent of men with HIV in a recent study experienced a persistent viral load in their genital secretions, suggesting that the female genital tract in particular may be a reservoir for the virus, aidsmap reports. A team of international investigators from the ACTG A5185s trial studied men and women with HIV from seven countries, including Brazil, India, Malawi, Peru, South Africa, the United States and Zimbabwe. They published their findings in the journal Clinical Infectious Diseases.

The investigators started the study participants on different combinations of ARVs and measured their respective blood and genital fluid viral loads at the beginning of the study and then after 48 and 96 weeks of treatment. Fifty-five percent of the men had HIV subtype B, and the remainder had subtype C. Seventy-six percent of the women had subtype C, and the rest subtype B. The median blood viral load was about 80,000 at the outset of the study, a figure that did not vary between the sexes. HIV was detectable in 82 percent of semen samples and 86 percent of cervical samples at the study baseline.

At the outset of the study, the women with subtype C of the virus had a median viral of about 125,000 in their genital tract, compared with 10,000 for the women with subtype B. Men with subtype C had a median viral load of 20,000 in their semen, compared with a seminal viral load of 6,000 for men with subtype B.

Sixteen percent of women and 6 percent of men had a detectable viral load in genital secretions at week 48 of the study. By week 96, the women still had a 16 percent rate of detectable viral load in genital secretions, compared with only 3 percent of men. Women with subtype C of the virus maintained their higher comparative levels of detectable viral load in cervical samples.

These findings notwithstanding, an increasing body of research has found that transmitting HIV between members of heterosexual couples is highly unlikely if the HIV-positive partner has an undetectable viral load in the blood as a consequence of ARV treatment.

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To read the study abstract, click here.