Estimated percentages and characteristics of men who have sex with men and use injection drugs--United States, 1999-2011.

Male-to-male sex and illicit injection drug use are important transmission routes for human immunodeficiency virus (HIV) infection. Of all new HIV infections in 2010, 80% were among men, of which 78% were among men who have sex with men (MSM), 6% among male injection drug users (IDU), and 4% among men who have sex with men and inject drugs (MSM/IDU). MSM/IDU might have different prevention needs from men who are either MSM or IDU, but not both. A combination of effective, scalable, and evidence-based approaches that address male-to-male sex and injection drug use behaviors might reduce HIV infections among MSM/IDU. To refine calculations of disease rates attributed to MSM and IDU by accounting for MSM/IDU, CDC used data from 1999-2008 National Health and Nutrition Examination Survey (NHANES) to estimate the percentage and number of MSM/IDU in the general population. To further describe demographic similarities and differences of MSM/IDU identified by different surveillance systems, CDC also compared data from four HIV surveillance systems: the 2008 and 2009 National HIV Behavioral Surveillance System (NHBS), the 2011 National HIV Surveillance System (NHSS), and the 2007-2009 Medical Monitoring Project (MMP). Of males aged ≥ 18 years, MSM/IDU comprised an estimated 0.35% in NHANES, 7%-20% in NHBS, an estimated 4%-8% in NHSS, and 9% in MMP. Across surveillance systems, MSM/IDU accounted for 4%-12% of MSM and 11%-39% of male IDU. Risk reduction programs and interventions targeted toward male IDU populations might be more effective if they also incorporate messages about male-to-male sex.