At this week’s National STD Prevention Conference in Atlanta, researchers presented data that shed light on the stark disparities in the rates of HIV infection among gay and bisexual men and other populations.

Researchers at the Centers for Disease Control employed a new method to evaluate just how hard hit men who have sex with men (MSM) are by HIV, as well as syphilis. Instead of just counting the numbers of new MSM infections, the researchers took the data that had already been collected and applied it to the presumed total number of MSM to determine the rate of infection among the entire community.

With the new analysis, researchers found that the frequency of gay/bisexual men who are diagnosed with HIV is 40 times that of heterosexual men and women.

Dr. Jonathan Mermin, director of CDC’s Division of HIV/AIDS Prevention, said the researchers estimated that MSM comprise approximately 2 percent of the entire country’s population.

“We used a methodology called meta-analysis, which looked at high-quality studies published in scientific literature that were nationally representative of men who’d had sex with men either during their lifetime or in the previous five years or one year,” Mermin said. “We felt the best estimate for our purposes would be in the prior five years, so we combined the data in a scientifically accurate way to come up with the fairly accurate 2-percent estimate, which is consistent with other estimates we’ve seen over the last few years.”

Using that estimate and current infection numbers among MSM, researchers calculated that there were between 522-989 cases of new HIV diagnoses per 100,000 MSM. For heterosexual men, there were just 12 cases of HIV and 13 for women in the same sample size. According to this analysis, the rate of MSM diagnoses is about 44 times that of heterosexual men and 40 times that of women.

Likewise, the researchers found that there were between 91-173 cases of primary and secondary syphilis per 100,000 MSM, but only two for heterosexual men and one for women, accounting for a rate of MSM diagnoses of 46 times that of other men and 71 times that of women.

“Calculating the actual rates allowed us to show the disparities between the prevalence of HIV infection among different groups,” Mermin said. “It allowed us to show that MSM have dramatically higher rates of HIV infection and syphilis infection compared to other men or women, and it’s very unusual to have such a large disparity.”

Mermin said the CDC is currently working on a more detailed analysis of MSM by race and age, but these preliminary numbers were startling.

“When I look at the rate of HIV among MSM as 44 times the rate of other men, that’s a tragedy, and it’s a clarion call for me, my division and the CDC in general to respond more effectively to the epidemic,” he said. “We need to provide accurate information to the public, the gay community and activists and we all need to start thinking more carefully about how we’re concentrating our resources for effective interventions and research that will allow new interventions to specifically help gay and bisexual men.”

Mermin noted several factors influencing the high rates of HIV among MSM.

“Certainly one of the most important variables is that there is a high prevalence of HIV and STDs among MSM, so if I were to meet a new male partner and have a relationship with that person, the chance that that person will be infected is far greater than it would be if I were a heterosexual man or a woman. And we also know that STDs like syphilis, gonorrhea and chlamydia, which are more common among MSM, increase someone’s chance of acquiring or transmitting HIV four-fold. And then there’s also the efficiency of transmission of penile-anal sex versus penile-vaginal sex. So not only is it more likely that a new partner will have HIV, it’s also more likely that you would be able to acquire it from them than someone else would be.”

Mermin added that numerous behavioral and social elements could impact the high rates, such as MSM’s tendency to have more sexual partners than heterosexuals, the prevalence of substance abuse, and the pervasive discrimination and homophobia that can prevent MSM from receiving adequate medical care.

There are several steps MSM should take to reduce their risk, Mermin said, such as decreasing their number of sexual partners, practicing safe sexual behaviors and being screened for HIV and STDs once a year, or more frequently if they’re at increased risk.

Mermin said knowing you’re infected with HIV often leads to a 60-percent reduction in risky sexual behaviors, and disclosing your status to a non-infected partner dramatically increases the chances that condoms will be used, which can decrease the risk of transmission by 90 percent.

Many young MSM have developed a complacent attitude toward the disease, Mermin said, recommending they get involved in HIV-prevention efforts to see firsthand that the disease is still having a significant impact on the MSM community.

“Treatment for HIV has become dramatically more effective in the past two decades, and because people can live long, healthy lives, some people don’t see HIV as serious an illness as they might have in the past,” he said. “Prevention in the HIV epidemic has been led by gay and bisexual men since the beginning of the epidemic, and I’d encourage all gay and bisexual men to stay active in those activities to keep it as an important part of their lives, because this still affects this community so tremendously. These are just remarkable disparities, and it’s very rare that there is any illness at all in the United States where you’d see such a high rate among one population over others.”

Jen Colletta can be reached at jen@epgn.com.