A new study now reveals that bisexual men are most at risk from HIV and other sexually transmitted diseases.

Gay Star News reports that the Centers for Disease Control and Prevention (CDC) released their findings in the American Journal of Preventative Medicine

William Jeffries, the author of the study, said that although HIV is less common in bisexual men, because they are often on the "down low," having sex with men but in relationships with a women, they are less likely to get tested for HIV, causing a greater risk. "Biphobia," he said, is to blame.

"Biphobia can manifest in erroneous beliefs that MSMW are gay men who have not disclosed their sexual orientation and, particularly for black men, responsible for HIV transmission to women," said Jeffries. "Experiencing these sentiments can contribute to [their] social isolation and psychological distress, which in turn may promote HIV/STI risk through substance use, sexual risk behaviors and the avoidance of prevention services."

Although Jeffries estimates that only two percent of the population identify as bisexual men, more outreach is needed to understand their sexual health factors including unprotected sex, forced sexual encounters and an increased number of sexual partners.

These findings shed further light on the November 2013 results from the University of Pittsburgh Graduate School of Public Health that reports, which challenged the long-held popular assumption that bisexual men were predominantly responsible for transmitting HIV to female partners.

"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," 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.

Researchers there analyzed more than 3,000 studies to gather data on HIV prevalence and the risks of HIV transmission between gay and bisexual men. They found that bisexual men were only 40 percent as likely to be infected with HIV as gay men. Friedman said that he believed men who were bisexual had a lower risk of HIV infection.