HIV service integration in substance use treatment facilities in the fentanyl era, 2015–2023

Illicitly manufactured fentanyl has reshaped the overdose crisis in the United States (US), driving unprecedented mortality while altering injection practices in ways that heighten HIV transmission risk among people who use drugs. Integrated HIV services within substance use disorder (SUD) treatment facilities represent a critical intervention point for this syndemic, yet whether service availability expanded commensurately with fentanyl’s geographic diffusion remains unknown. We conducted a longitudinal, county-level study of US counties from 2015 to 2023 using geocoded facility listings from the National Survey of Substance Abuse Treatment Services (and the National Substance Use and Mental Health Services Survey). The outcome was the annual county-level proportion of SUD treatment facilities reporting HIV services. Longitudinal growth models with a beta distribution estimated rates of change before and after the state-specific onset of rapid illicit fentanyl market penetration, derived from National Forensic Laboratory Information System data. Time-varying covariates included county-level drug overdose mortality and HIV incidence rates (both two-year lagged), Medicaid expansion, and state medication for opioid use disorder prior authorization prohibitions. From 2015 to 2023, the average proportion of SUD facilities providing HIV services doubled among counties with existing treatment infrastructure. County-level changes were geographically heterogeneous: following fentanyl introduction, HIV service availability increased in 38.8% of counties, remained stable in 14.0%, decreased in 24.5%, and was unavailable in 22.7% because SUD treatment facilities were absent. In adjusted models, the increase in HIV services pre-fentanyl was not statistically significant (β = 0.021; SE = 0.013), whereas service integration accelerated after fentanyl detection (post-fentanyl slope β = 0.072; SE = 0.009; P < .001), with a significant slope-by-fentanyl interaction (β = 0.051; SE = 0.014; P < .001). SUD treatment facilities expanded HIV services more rapidly following state-level fentanyl introduction, suggesting adaptive integration of HIV prevention and care within addiction treatment systems during the fentanyl era. However, persistent geographic disparities and no in-person treatment infrastructure in nearly one-quarter of US counties represent critical barriers to equitable access to integrated services, underscoring the need for policies that expand SUD treatment capacity and incentivize HIV service integration in underserved communities.