Illegally manufactured fentanyl might be driving transmission of hepatitis C virus (HCV), with use linked to a 64% greater risk of acquiring the viral infection, according to study results published in Clinical Infectious Diseases.

"The broad shift from heroin to illicit fentanyl may be playing an important role in sharply rising HCV incidence among young people in recent years,” Joseph Friedman, MD, PhD, of the University of California San Diego School of Medicine, said in a press release. “HCV elimination has been prioritized as a goal of the White House, and these findings suggest that accomplishing that goal may require taking a closer look at the role of fentanyl and other synthetic drugs in driving infectious disease risks.”

Sharing needles and other equipment for drug use is a major risk factor HCV transmission. While fentanyl is linked to higher rates of death due to overdose, its impact on the spread of infectious diseases like HCV and HIV is unclear. Friedman and colleagues assessed whether fentanyl use could predict HCV and HIV prevalence among people who inject drugs in San Diego and Tijuana, Mexico.

From 2020 to 2022, the research team recruited people who inject drugs and asked them to participate in semi-annual interviewer-administered surveys as well as testing for the two viruses through 2024. 

The study included 398 people. The median age was 43 years, 70% were men and two thirds lived in San Diego. About 40% said they engaged in receptive needle sharing, and 25% said they used illegally manufactured fentanyl.

The researchers noted that hepatitis C incidence was 14.26 cases per 100 person-years and HIV incidence was 1.29 cases per 100 person-years. Fentanyl use was linked to a 64% higher risk of contracting HCV. While the risk of HIV trended in the same way, the link was not statistically significant.

The researchers suggest that fentanyl’s short half-life in the body, or the time it takes for a half dose to be metabolized, may drive more repeated sharing of needles and smoking equipment.

“Our study provides the first evidence that illicit fentanyl use is linked to an increased risk of acquiring hepatitis C infection, which disproportionately affects people who inject drugs,” lead author Steffanie Strathdee, PhD, also of the UC San Diego School of Medicine, said in the press release. “This underscores the importance of making point-of-care HCV viral load testing more widely available in the United States, so those needing treatment can access it immediately.”

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