Although research to date shows that the insertive partner during anal sex is at a much lower risk of HIV infection than the receptive partner, a new study in the July 1 edition of The Journal of Infectious Diseases suggests that the risk to "tops" may be higher than previously thought. Levels of HIV RNA detected in rectal mucosa secretions of 64 HIV-positive gay and bisexual men were shown to be much higher than viral levels in their blood and semen; HIV was still detected in the secretions even when blood-based viral loads were undetectable, the researchers report.
HIV viral loads were measured in the blood, in semen, and from rectal mucosal secretions from the study subjects, about half of whom were taking antiretroviral drugs and the remainder of whom were treatment-naive. The median viral load detected in the study subjects' blood was 17,400 copies, and the median semen-based viral load was 3,550. This compares with a median 91,200 viral copies detected in rectal secretions. When limiting the study to only HIV-positive men taking anti-HIV drugs, the same pattern of viral loads were observed--HIV RNA levels in rectal secretions remained significantly higher than those in the blood or in semen. Among treatment-naive patients, 35 of 37 study subjects had detectable HIV RNA in their rectal secretions.
Although receptive anal sex is still considered by AIDS experts to carry the highest risk for HIV infection because small tears in the rectum can allow HIV in semen to easily pass into the body, this new study suggests insertive partners may be at a higher risk than originally believed. This may be particularly true for men who are uncircumcised; previous studies have shown that uncircumcised men are at a higher risk for HIV infection because semen, rectal secretions, and vaginal secretions can remain trapped under the foreskin and placed in prolonged contact with penile tissue.