The agencies surveyed 29 black men ages 17 to 25 who had tested positive for H.I.V. between 2006 and 2008 and who reported having sex with other men. Twenty reported having unprotected anal intercourse with a man during the year before their positive H.I.V. tests, and 16 reported having male sex partners who were 26 or older.
Having older sex partners increases the risk of infection because older men are more likely than younger men to be infected.
Only three of the 29 men thought it likely they would acquire H.I.V. during their lifetime. More than half thought it unlikely or very unlikely, the survey found.