HIV: While only about 4% of U.S. males have sex with other men, they represent about two-thirds of the country’s new infections, according to the CDC

In 2010, about 73% of new infections were in people 13 to 24 years old, the CDC says. In a recent study, researchers analyzed patterns of new HIV infections among 594 young men who have sex with men. Participants were recruited from the New York City area between 2009 and 2011 and were 18 or 19 when they entered the study. At that point they were all HIV-negative. Over the next three years, 43 participants became infected with HIV. About a third of black, Hispanic and mixed or other race participants became HIV-positive during the study, compared to about 7% of white participants. Also, the researchers found, young age at first sexual experience with another male was tied to an increased risk of becoming HIV-positive, compared to a first encounter at an older age.