The number of HIV positive men who have sex with both men and women is likely no higher than the number of HIV positive heterosexual men, according to a U.S.-based analysis by University of Pittsburgh Graduate School of Public Health researchers. The finding challenges a popular assumption that bisexual men are responsible for significant HIV transmission to their female partners.

The research, which will be presented today at the American Public Health Association’s 141st Annual Meeting & Exposition in Boston, builds a case for federal investment in research on HIV prevalence among bisexually behaving men.

“Some observers have exaggerated the idea of viral ‘bridging’ - where a bisexual man contracts HIV from another man and then transmits it to a female partner. But, at least in the U.S., the data supporting the extent of this is quite limited,” said Mackey R. Friedman, Ph.D., M.P.H., of Pitt Public Health’s Department of Infectious Diseases and Microbiology, who led the research.

Currently, the U.S. Centers for Disease Control and Prevention (CDC) does not report on HIV data specific to bisexually behaving people, though it does report data on homosexually and heterosexually behaving people, as well as injection drug users.

Dr. Friedman and his colleagues reviewed over 3,000 scientific articles to obtain data on HIV prevalence and risks among men who have sex with men only and men who have sex with men and women.

The bisexually behaving men were only 40 percent as likely to be infected with HIV as the homosexually behaving men. The researchers propose that this is because the bisexually behaving men reported lower rates of unprotected receptive anal intercourse, the biggest risk factor for HIV transmission among men in the U.S.

The analysis also estimates that there are approximately 1.2 million bisexual men in the U.S., of whom 121,800 are HIV-positive. That estimate aligns with CDC estimates for HIV infection in male heterosexuals and intravenous drug users.

Dr. Friedman, who has conducted HIV prevention and research for more than 15 years, believes that while bisexually behaving men may have a lower risk profile than homosexually behaving men, their HIV burden still warrants the development of targeted interventions.

“The HIV infection risk that bisexual men pose to their female partners has likely been overstated,” said Dr. Friedman. “However, that doesn’t mean that HIV-prevention campaigns targeting bisexual men and their male and female partners aren’t needed. HIV does exist in the bisexual community, and national, bisexual-specific data collection, research, and HIV prevention and care delivery are necessary to ameliorate this population’s HIV burden.”

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Additional collaborators on this research are Chongyi Wei, Dr.P.H., Mary Lou Klem, Ph.D., Anthony Silvestre, Ph.D., Nina Markovic, Ph.D., and Ron Stall, Ph.D., all of the University of Pittsburgh.

About the University of Pittsburgh Graduate School of Public Health

The University of Pittsburgh Graduate School of Public Health, founded in 1948 and now one of the top-ranked schools of public health in the United States, conducts research on public health and medical care that improves the lives of millions of people around the world. Pitt Public Health is a leader in devising new methods to prevent and treat cardiovascular diseases, HIV/AIDS, cancer and other important public health problems. For more information about Pitt Public Health, visit the school’s Web site at http://www.publichealth.pitt.edu. http://www.upmc.com/media

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