| Non-injecting heroin users (NIHU) who transition to drug injection will help shape the future course of the HIV/AIDS epidemic and the spread of hepatitis B (HBV) and C (HCV) in the U.S. We examine (1) the extent of former injection drug use among young NIHU, (2) the incidence and predictors of injection transitions, and (3) the prevalence, incidence, and risk of HIV, HBV and HCV infections.;NIHU 16-30 years old were recruited in Chicago through street outreach and respondent-driven methods for a prospective cohort study. Computerized self-administered interviews collected self-report data at baseline and subsequent follow-up visits scheduled at 6-month intervals for up to 3 years. Logistic regression analysis assessed factors associated with history of injection at baseline. Person-time methods estimated incidence rates and Cox proportional hazards regression examined predictors of transitions to injection and HIV, HBV, and HCV seroconversions.;Of 689 NIHU, 51.2% were non-Hispanic(NH) Black, 64.4% male, and the median age was 25. Former injection was reported by 17.9% and of those, 66.7% injected <10 times. At follow-up, 561 (81.4%) returned for ≥1 visit. Transition to drug injection during follow-up was reported by 154 (27.5%, rate 14.7 per 100 person-years[py]) participants. The rate was significantly (p<0.001) higher among former injectors compared to never injectors. Multivariable analysis identified individual, drug use, and social factors that predicted injection transitions among young NIHU. Finally, of those initially at risk for infection, 1 (0.2%, rate 0.08 per 100py) participant seroconverted for HIV during follow-up, 11(2.6%, rate 1.2 per 100py) for HBV and 27 (5.0%, rate 2.3 per 100py) for HCV. Those with greater sexual risk exposure were at increased risk for HIV and HBV, and those who transitioned to injection at follow-up were at high-risk for HCV seroconversion.;We detected a high rate of transitions to injection among young NIHU. The risk of injection was greatest among former injectors and NH-Whites, and least among NH-Blacks. Furthermore, we report individual, drug behavior and social factors that identify at-risk users and that can be used for developing intervention programs aiming to prevent injection and the transmission of HIV, HBV, and HCV infections among drug users. |
