Researchers examining injection drug users (IDUs) in drug treatment have been trying for decades to determine the optimal way to intervene to prevent the transmission and spread of human immunodeficiency virus (HIV) in this population. Although efficacious HIV risk reduction interventions are widely available, questions remain about what specific factors are most related to HIV risk behavior and defined as unprotected sexual activity and/or high risk drug use. This review involved an evaluation of the research literature in order to better understand the association between drug use and sexual behavior debut on HIV risk behavior. Findings suggest that drug use debut and sexual behavior debut may be related to subsequent HIV risk behavior. Evidence to date implies that intervening at an earlier age to assist youth to avoid or delay these high risk behaviors may be an additional means of reducing subsequent HIV risk. 1. Introduction Globally, an estimated 3 million people who inject drugs are living with HIV, representing roughly one in 10 infections worldwide [1]. An estimated 49,273 individuals in the U.S. were infected with HIV in 2011 and injection drug users (IDUs) remain at high risk for HIV transmission. Since the epidemic began, nearly 182,000 injection drug users with an AIDS diagnosis have died, including an estimated 4,218 in 2010. Of the approximate 32,050 new cases of AIDS reported in 2011, 3,961 were IDU-associated. In 2011, 7.4% of all newly diagnosed cases in adults and adolescents were from IDU-associated behavior [2]. With the high rate of HIV risk in the IDU population, it is even more important to understand the events leading to risk behavior. Part of the global HIV epidemic involves adolescents who are initiating sexual activity at progressively earlier ages [3] and putting themselves and others at increased risk for HIV infection. A 2011 CDC survey found that 47% of high school students reported having sexual intercourse, 6.2% reported having intercourse before age 13, and an alarming 39.8% reported not using a condom during their last intercourse [4]. The average reported age of first sexual intercourse in the USA is age 14.4, with more males than females (9.0% versus 3.4%, resp.), and more African-American teens than other racial/ethnic groups reporting sexual activity before age 13—highlighting a common racial disparity pattern [4, 5]. Although data exist regarding HIV risk and prevalence rates, questions remain about what factors are most predictive of subsequent HIV risk behavior among adolescents and young adults, and thus
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