Between 2005 and 2011, the rate of men who have sex with men (MSM) who reported having unprotected anal intercourse (UAI) in the past year increased by 20 percent, The New York Times reports. However, sexual risk-taking in 2011 was dramatically lower among those MSM who accurately knew their HIV status.

Publishing their findings in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report (MMWR), CDC investigators pooled data from surveys taken in 20 major U.S. cities. The surveys are part of the ongoing National HIV Behavioral Surveillance System, which studies sexual risk-taking as well as HIV testing and prevalence in three-year cycles that rotate between MSM, injection drug users and high-risk heterosexuals.

In 2005, 48 percent of the study participants reported UAI at least once in the past year, a figure that rose to 57 percent in 2011. The CDC theorizes that part of the reason for this increase may be that MSM are “serosorting”: attempting to have UAI only with men of their same HIV status. The federal health agency cautions, however, that such a strategy has major pitfalls, because HIV-positive men “might not know or disclose that they are infected, and men’s assumptions about the HIV status of their partners can be wrong.”

On average, MSM had serodiscordant UAI—unprotected sex with someone of a different serostatus—during their last encounter at a rate of 13 percent in both 2008 and 2011. A third of those in the 2011 cohort who had HIV but did not know it until they were diagnosed during the survey reported serodiscordant UAI during their last sexual experience. By comparison, just 12 percent those who knew they were HIV-positive had serodiscordant UAI the last time they had intercourse and 13 percent of those who were HIV-negative did so.  

A third of MSM reported that they had not received an HIV test in the previous year. Of those who were tested during the previous 12 months, 5 percent of those who either didn’t know their status or who reported being HIV negative received a diagnosis of HIV as a result of their participation in the survey.

To read the CDC release, click here.

To read the MMWR, click here.

To read the Times story, click here.