Researchers from the University of Pittsburgh Graduate School of Public Health say that the number of HIV-positive men in the US who have sex with both men and women is likely to be equal to the number of HIV-positive men who only have sex with women.
Their research, presented at the American Public Health Association's 141st Annual Meeting and Exposition in Boston, MA, is thought to challenge the "popular assumption" that men who are bisexual are predominantly responsible for transmitting HIV (human immunodeficiency virus) to female partners.
At present, the Centers for Disease Control and Prevention (CDC) has no data detailing HIV prevalence within bisexual populations in the US, but the researchers note the CDC does hold data on HIV prevalence within homosexual and heterosexual populations.
"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 US, the data supporting the extent of this is quite limited," says Dr. Mackey R. Friedman, of the Department of Infectious Diseases and Microbiology at the University of Pittsburgh Graduate School of Public Health and lead author of the study.
Bisexual men '40% as likely' to be infected as homosexual men
To reach their findings, the researchers analyzed more than 3,000 studies to gather data on HIV prevalence and the risks of HIV transmission between men who have sex with women only, and men who have sex with both men and women.
From the analysis, the researchers estimate that there are around 1.2 million bisexual men in the US. Of these, they estimate that 121,800 are HIV-positive.
The researchers say these figures aligned with CDC estimates of HIV infection in male heterosexuals and intravenous drug users in the US.
Furthermore, the analysis revealed that men who were bisexual were only 40% as likely to be infected with HIV as men who were homosexual.
The researchers hypothesize that this is because men who were bisexual reported lower rates of unprotected receptive anal intercourse. According to the researchers, this is the largest risk factor for HIV transmission among US men.
Dr. Friedman says that while he believes men who are bisexual have lower risk of HIV infection, compared with men who are homosexual, there still need to be interventions in place to reduce the HIV burden.
"The HIV infection risk that bisexual men pose to their female partners has likely been overstated.
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."
The researchers say they hope their findings encourage federal bodies to invest in research surrounding HIV prevalence in men who are bisexual.
Medical News Today recently reported on a study detailing the discovery of a protein that plays a key role in HIV infection.