Participants who used fentanyl were 1.64 times more likely to experience HCV seroconversion compared to those who did not.
Joseph Friedman, MD, PhD, MPH
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A recent study has found an association between illicit fentanyl use and an increased risk of hepatitis C virus (HCV) infection among people who inject drugs (PWID) in San Diego, California, and Tijuana, Mexico. The study followed a cohort of 398 PWID from 2020 to 2022 to examine whether illicit fentanyl (IMF) use is linked to HCV and human immunodeficiency virus (HIV) transmission.
The researchers found that participants who reported using illicit fentanyl were 1.64 times more likely to experience HCV seroconversion—an indicator of a new infection—compared to those who did not use fentanyl. After adjusting for other factors, the hazard ratio remained at 1.57, indicating a significant association between IMF use and new HCV infections. The study recorded an HCV incidence of 14.26 cases per 100 person-years, compared to 1.29 for HIV.
In an exclusive interview with Contagion, Joseph Friedman, MD, PhD, MPH, lead author of the study, explained that the short half-life of illicit fentanyl could contribute to this increased risk. “The short half-life of illicit fentanyl means that people who become dependent on it often find themselves having to use it much more frequently than they would other opioids such as heroin. This means injecting or smoking more times per day. Increased use frequency can add logistical complexity to the day and promote sharing syringes, smoking, or drug preparation materials, which can transmit infectious diseases, such as HCV.”
The study also explored the relationship between IMF use and HIV, but the results were less conclusive. Only 10 participants in the study experienced HIV seroconversion, which limited the ability to establish a clear connection between IMF use and HIV risk. Friedman noted that larger studies with higher sample sizes in regions with greater HIV prevalence may help clarify this potential link. “We hypothesize that if we had a larger sample size, we might have found a similar and significant association between HIV and fentanyl to what we saw with HCV and fentanyl. We will need more data to be sure. But we did see a similar direction of association. This is an important area for future research.”
The study's design, which includes participants from both San Diego and Tijuana, highlights the challenges of addressing fentanyl-related infectious disease transmission in border regions. Friedman emphasized that infectious disease transmission in these areas should be viewed as a binational issue. Friedman explains that drug use and infectious disease spread in these areas should be understood as a "binational phenomenon.”
The study found that people who used illicit fentanyl were 1.64 times more likely to experience HCV seroconversion compared to those who did not.
The study found inconclusive results regarding the link between fentanyl use and HIV due to the small number of HIV cases observed.
The study highlights the need for improved cross-border healthcare and harm-reduction strategies like syringe exchange programs in regions like San Diego and Tijuana.
“Our research team has shown that infectious disease transmission in this area needs to be understood as a binational phenomenon. Many people cross the border to use drugs or participate in sex tourism, which drives the spread of infectious diseases such as HIV or HCV. Although HCV elimination is a stated goal of the governments of both countries, more needs to be done to reduce barriers to accessing treatment in practice,” he explained.
Based on the findings, Friedman recommended harm-reduction strategies, such as syringe exchange programs and supervised injection sites, as ways to reduce the transmission of HCV among people who inject drugs. “Syringe exchanges, and teaching safe injection practices are, of course, an important and evidence-based strategy. Also, given that we are now in the era where HCV is a curable condition, we need to greatly expand access to curative treatment, to reduce the continued spread of the disease. There are many individuals living with HCV, especially those who use drugs, who are unable to access treatment due to logistical, bureaucratic, and/or financial barriers.”
This study contributes to the ongoing understanding of the public health challenges associated with illicit fentanyl use, particularly in regions where injection drug use is prevalent. The findings highlight the importance of addressing opioid use and infectious disease prevention as part of comprehensive public health strategies. The research also points to the need for additional studies, especially those that explore the potential relationship between fentanyl use and HIV transmission.
