By Joseph R Friedman, Daniela Abramovitz, Britt Skaathun, Gudelia Rangel, Alicia Harvey-Vera, Carlos F Vera, Irina Artamonova, Sheryl Muñoz, Natasha K Martin, William H Eger ...

Background

Illicitly manufactured fentanyl (IMF) increases overdose mortality, but its role in infectious disease transmission is unknown. We examined whether IMF use predicts hepatitis C virus (HCV) and human immunodeficiency virus (HIV) incidence among a cohort of people who inject drugs (PWID) in San Diego, California and Tijuana, Mexico.

Methods

PWID were recruited during 2020–2022, undergoing semi-annual interviewer-administered surveys and HIV and HCV serological rapid tests through 2024. Cox regression was conducted to examine predictors of seroconversion considering self-reported IMF use as a 6-month lagged, time-dependent covariate.

Results

Of 398 PWID at baseline, 67% resided in San Diego, 70% were male, median age was 43 years, 42% reported receptive needle sharing, and 25% reported using IMF. HCV incidence was 14.26 per 100 person-years (95% confidence interval [CI]: 11.49–17.02), and HIV incidence was 1.29 (95% CI: .49–2.10). IMF was associated with HCV seroconversion, with a univariable hazard ratio (HR) of 1.64 (95% CI: 1.09–2.40), and multivariable HR of 1.57 (95% CI: 1.03–2.40). The direction of the relationship with HIV was similar, albeit not significant (HR 2.39; 95% CI: .66–8.64).

Conclusions

We document a novel association between IMF and HCV seroconversion among PWID in Tijuana–San Diego. Few HIV seroconversions (n = 10) precluded our ability to assess if a similar relationship held for HIV. IMF's short half-life may destabilize PWID—increasing the need for repeat dosing and sharing smoking materials and syringes. New preventive care approaches may reduce HCV transmission in the fentanyl era.

Clinical Infectious Diseases, cia e372, 2024.