San Francisco Chronicle Examines How Sero-Sorting Might Contribute to Decreasing HIV Incidence Among City’s MSM
The San Francisco Chronicle on Sunday examined how sero-sorting -- the practice in which people who know their HIV status search for partners of the same status -- might be helping to reduce the incidence of HIV among men who have sex with men in San Francisco (Heredia, San Francisco Chronicle, 2/12). A CDC study released in June 2005 found San Francisco's HIV-incidence rate among MSM has decreased by nearly half in the last four years. The study, based on a survey of 365 MSM who were tested in the city, found an annual incidence rate of 1.2%, compared with city epidemiologists' previous estimate of 2.2%. The study led the San Francisco Department of Public Health's Office of AIDS to analyze data sets collected by the Stop AIDS Project, as well as surveys of new cases at city clinics, both of which indicated a similar decrease in the number of new HIV cases. Although some health officials attribute the decline in incidence to conventional efforts, other experts say that an increase in the number of MSM participating in sero-sorting might be contributing to the decrease in new HIV cases (Kaiser Daily HIV/AIDS Report, 8/18/05). Mitch Katz, San Francisco's public health director, said, "Sero-sorting is happening. It's working. It's one of the explanations we have for the flattening of the (HIV) seroincidence curve." He added that sero-sorting is an effective HIV-prevention method for HIV-positive and HIV-negative couples because it "enables men to have the sex they want without worrying about contracting HIV." Increased access to antiretroviral drugs also might be contributing to the city's decreasing HIV incidence among MSM because HIV-positive people are less likely to transmit the virus to their sexual partners when adhering to a treatment regimen, according to Katz.
Researchers at the University of California-San Francisco's Gladstone Institute of Virology and Immunology currently are conducting a study to look for evidence of "superinfection," infection with more than one HIV strain in a single person, among HIV-positive MSM who participate in sero-sorting. The study, called the Positive Partners Study, began five years ago and has enrolled 176 participants, most of whom are MSM who do not use condoms. Preliminary results from the study suggest that although superinfection is rare, it does occur. Four of the study participants have shown signs of superinfection, which include a declining CD4+ T cell count and increasing viral load, according to the Chronicle. All four men have been HIV-positive for fewer than three years (San Francisco Chronicle, 2/12).