In part, these differences reflect the fact that an individual MSM can engage in both insertive and receptive sexual roles (i.e., versatility), while exclusively heterosexual men and women each engage in only one of these roles.
The Centers for Disease Control and Prevention (CDC) estimates that HIV and early syphilis rates among MSM are >40 times higher than those among heterosexuals 4. population 1, but accounted for 59% of new HIV infections and 62% of cases of early syphilis in 2009 2, 3. MSM comprise approximately 2% of the U.S. Sexually transmitted infections (STI) disproportionately affect men who have sex with men (MSM).
