Q&A: Illicit fentanyl use raises hepatitis C risk among injection drug users
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Key takeaways:
- Use of illicit fentanyl increased injection drug users’ risk for hepatitis C by more than 60%.
- The finding has implications for HCV control, according to researchers.
A new study provides the first evidence that illicit fentanyl use may play a role in hepatitis C transmission among injection drug users, according to researchers.
The finding, reported in Clinical Infectious Diseases, “raises important considerations” for HCV control, the researchers said.
In a 3-year study, the researchers recruited and tested nearly 398 adult injection drug users in San Diego and Tijuana, Mexico, where illicitly manufactured fentanyl “has broadly overtaken the drug supply.” Around one-quarter of the study participants reported using illicitly manufactured fentanyl.
In all, 102 participants acquired HCV during the study period. Participants who used illicit fentanyl faced a 64% higher risk for HCV compared with those who did not, the researchers reported.
The researchers also planned to assess whether illicit fentanyl use increased the risk for HIV, but a low number of new infections among participants — just 10 — prevented them from being able to determine if there was a relationship.
To learn more about the study and what it showed, we sent some questions to Steffanie Strathdee, PhD, professor and researcher at the University of California, San Diego School of Medicine.
Healio: You suggest there may also have been an association between illicit fentanyl use and HIV that the study did not pick up because of the small number of HIV infections that occurred among participants. Is there a larger study planned that might be able to demonstrate an association?
Strathdee: Our current NIH-funded study ends in January 2025, but we have a submitted grant proposal that we hope will be funded so we can continue to follow our binational cohort.
Healio: What about other pathogens? San Diego had a large outbreak of hepatitis A not long ago. Did you consider examining whether illicit fentanyl use also had any impact on infections other than HCV or HIV?
Strathdee: We are currently focused on pathogens that are spread parenterally or sexually. While people who use drugs are at high risk for hepatitis A, the transmission route is oral-fecal so it is unlikely to have a direct link to a specific type of drug used.
Healio: You said more research is needed to understand the mechanisms at work here. What do you think could explain the association between illicit fentanyl use and hepatitis C?
Strathdee: For people who inject drugs, the mechanism is clear. We know people who inject drugs who share paraphernalia are at high risk for transmitting HCV and HIV. We also know that fentanyl’s short half-life means that people who are addicted to it inject more frequently, which heightens their risk for bloodborne infections. And we have also shown that people who inject fentanyl are less able to ensure that they inject with sterile equipment.
HCV is 10 times more infectious than HIV through shared injection paraphernalia, and HCV has a longer half-life than HIV, so the short half-life of fentanyl and the long half-life of HCV make for a deadly combination. However, we also found that fentanyl use was independently associated with HCV, even among people who were not injecting drugs, so further study is needed to determine why. It could be that fentanyl use is a marker of a riskier lifestyle, but it is also possible that sharing noninjection equipment like straws and dollar bills used to inhale it could transmit HCV.
Healio: What other questions were not answered by the study?
Strathdee: We weren’t able to determine whether fentanyl use increases HIV transmission, or to determine the mechanism for HCV transmission among those not injecting fentanyl.
Healio: What are the implications of these findings inside and outside of San Diego and Tijuana?
Strathdee: Both the U.S. and Mexico have federal plans to eliminate HCV, so policymakers in both countries should be made aware that fentanyl is playing a role in ongoing HCV transmission, and federal programs like the [NIH’s] HEAL Initiative that tackle opioid addiction should be aware that fentanyl use doesn’t just increase the risk for overdose, it increases the risk for acquiring HCV.
Healio: What should the public health response to this be?
Strathdee: Our findings have implications for both the treatment of opioid addiction and HCV.
First, efforts should be made to expand medications for opioid use disorder (MOUD) like methadone and buprenorphine, and supply sterile syringes and safer smoking supplies to reduce risks. Only 10% to 15% of people with opioid use disorder are receiving MOUD in the U.S., which leaves a lot of room for improvement. In many states, harm reduction supplies are not available or are scarce, and smoking supplies have even been banned. Drug-checking services should be made available as well since the drug supply is toxic and many people who use drugs do not know if they are using fentanyl or not.
Second, expansion of point-of-care HCV testing is needed among marginalized populations like people who use drugs so we can improve the HCV continuum of care. The good news is that the FDA recently approved Cepheid’s rapid test that can detect HCV RNA. That is a great first step, because some people spontaneously clear the virus and don’t need treatment, whereas others with ongoing active infections are often unknowingly spreading the virus. However, this rapid HCV RNA test is approved only for adults aged 22 years and older, which excludes younger people who inject drugs who are usually infected with HCV within the first year or 2 after beginning to inject drugs. I’m hoping that this situation will be remedied soon because the sensitivity and specificity of a test like this does not differ with age.
Finally, once people are diagnosed with an active HCV infection, they need to be linked to care immediately. Mobile clinics could play a major role in expanding access to HCV treatment for people who use drugs who are often outside the health care system. Health departments should be equipped with all of these interventions.
References:
- CDC. Universal hepatitis C screening among adults and treatment for hepatitis C virus infection. https://www.cdc.gov/high-impact-prevention/php/case-studies/hepatitis-c-screening-treatment.html. Last updated April 23, 2024. Accessed Aug. 7, 2024.
- Friedman JR, et al. Clin Infect Dis. 2024;doi:10.1093/cid/ciae372.
- Illicit fentanyl use linked to increased risk of hepatitis C among people who use drugs. https://today.ucsd.edu/story/illicit-fentanyl-use-linked-to-increased-risk-of-hepatitis-c-among-people-who-use-drugs. Published July 30, 2024. Accessed Aug. 5, 2024.
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