Selection by men of sexual partners and behaviors according to HIV status, a phenomenon called serosorting, influences the spread of HIV and other sexually transmitted infections, according to a report in the December 2006 issue of Sexually Transmitted Infections.
"Prevention with positives is a promising point of intervention to slow the epidemic by preventing further transmission," Dr. Willi McFarland from the San Francisco Department of Public Health, California told Reuters Health. "With respect to serosorting in particular, physicians should be ready to discuss the implications of HIV-positive patients having unprotected sex with other HIV-positives."
Dr. McFarland and colleagues attempted to assess whether increases in HIV serosorting contribute to preventing further expansion of the epidemic and have other effects on other sexually transmitted diseases.
Despite decreases in the incidence of HIV infection among men who have sex with men (MSM) in San Francisco, the authors report, cases of rectal gonorrhea and early syphilis increased from 1998 to 2004.
Over this interval, there was an increase in unprotected anal intercourse, the results indicate, but the behavior decreased among HIV-negative and HIV-positive MSM with partners of unknown HIV serostatus.
"Our data support the hypothesis that MSM are increasingly selecting HIV seroconcordant partners when engaging in unprotected anal intercourse," the investigators say. "The choice of HIV negative people as the insertive partner, referred to as strategic positioning (or 'seropositioning') may reflect a second strategy to decrease HIV risk."
"There are other reasons why people may choose partners of the same serostatus beyond the risk of HIV transmission," Dr. McFarland explained. "For example, HIV-positive persons may find more support in a relationship with another HIV-positive person because they share many more of the challenging aspects of living with HIV."
The investigator concluded: "Our observations and studies of serosorting may simply be documenting the rise of a community-generated HIV prevention strategy that is happening whether we have any control over it or not." Dr. McFarland said.
Sex Transm Infect 2006;82:461-466.

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