Hepatitis C in people who inject drugs : prevalence, incidence, mortality, and treatment uptake

<p dir="ltr">Hepatitis C virus (HCV) infection can progress to liver cirrhosis and hepatocellular carcinoma (HCC) and was in 2022 estimated to cause 240,000 deaths worldwide. The virus is bloodborne, and a main transmission route is injection drug use through sharing of unsterile needles and syringes. The prevalence of HCV infection is consequently high in people who inject drugs (PWID). The World Health Organization (WHO) has set a goal to eliminate HCV as a public health threat, by the year 2030, which includes a 90% reduction in new chronic infections, a 65% reduction in mortality, and a target of >80% treated. To achieve this goal a deeper understanding of the epidemiology of HCV in PWID, the main drivers of the epidemic, is essential. The aims of this thesis were to study the prevalence and incidence of HCV infection, liver-related mortality, and HCV treatment uptake in PWID.</p><p dir="ltr"><b>In Study I</b>, we demonstrated a high prevalence of HCV infection (11%) in detainees in Stockholm County, which highlights that prisons could constitute a target facility for testing and treatment of HCV infection.</p><p dir="ltr"><b>In Study II</b>, we reported a high liver-related mortality in PWID with HCV infection. Amphetamine users had an even higher liver-related mortality than opioid users, probably as they lived longer and were less likely to die from drug-related causes at younger ages, which enabled late consequences of HCV infection to emerge. In addition, amphetamine users had a higher alcohol-consumption, which was a risk factor for liver-related death.</p><p dir="ltr"><b>In Study III</b>, we noted a great decline in HCV prevalence in PWID in Stockholm (from 62% to 30%) in recent years, following the introduction of direct-acting antiviral (DAA) treatment and the startup of a needle syringe program (NSP) in Stockholm. However, no significant reduction in incidence was observed, indicating that treatment efforts to date have primarily reached individuals with lower injection-related risk behaviors, while those at highest risk of onward transmission may remain untreated.</p><p dir="ltr"><b>In study IV</b>, we reported that >80% of individuals notified with HCV infection in Sweden have initiated treatment, indicating that Sweden has reached the WHO HCV treatment target. Median time to treatment initiation was only a few months in recent years. The odds of receiving treatment were, however, lower among people with drug use diagnoses.</p><p dir="ltr"><b>In conclusion</b>, this thesis demonstrates high HCV prevalence and incidence rates in PWID, as well as elevated liver-related mortality. Along with an increasing treatment uptake in recent years, the HCV prevalence has decreased, suggesting that a scale up of HCV treatment is effective. However, the lack of reduction in incidence among PWID highlights the importance of further expanded testing and treatment efforts. To achieve the WHO elimination goal, PWID need to remain a key focus, especially those with the highest risk behaviors for viral transmission, and high-prevalence settings such as prisons, NSPs, and addiction treatment centers should be targeted.</p><h3>List of scientific papers</h3><p dir="ltr">I. <b>Gahrton C,</b> Westman G, Lindahl K, Öhrn F, Dalgard O, Lidman C, Nilsson LH, Said K, Duberg AS, Aleman S. Prevalence of Viremic hepatitis C, hepatitis B, and HIV infection, and vaccination status among prisoners in Stockholm County. BMC Infect Dis. 2019;19(1):955. <a href="https://doi.org/10.1186/s12879-019-4581-3" rel="noreferrer" target="_blank">https://doi.org/10.1186/s12879-019-4581-3</a></p><p dir="ltr">II. <b>Gahrton C,</b> Håkansson A, Kåberg M, Jerkeman A, Häbel H, Dalgard O, Duberg AS*, Aleman S*. Mortality among amphetamine users with hepatitis C virus infection: A nationwide study. PLoS One.2021;16(6):e0253710. <a href="https://doi.org/10.1371/journal.pone.0253710" rel="noreferrer" target="_blank">https://doi.org/10.1371/journal.pone.0253710</a></p><p dir="ltr">III. <b>Gahrton C,</b> Navér G, Warnqvist A, Dalgart O, Aleman S, Kåberg M. Changes in hepatitis C virus prevalence and incidence among people who inject drugs in the direct acting antiviral era. International Journal on Drug Policy, 2024;128:104433. <a href="https://doi.org/10.1016/j.drugpo.2024.104433" rel="noreferrer" target="_blank">https://doi.org/10.1016/j.drugpo.2024.104433</a></p><p dir="ltr">IV. <b>Gahrton C,</b> Kåberg M, Lybeck C, Lindahl K, Patil S, Dalgard O, Aleman S*, Duberg AS*. Treatment uptake among individuals notified with HCV infection 1990- 2022 in Sweden. Infectious diseases. 2025:1-11. <a href="https://doi.org/10.1080/23744235.2025.2569504" rel="noreferrer" target="_blank">https://doi.org/10.1080/23744235.2025.2569504</a></p><p dir="ltr">*shared last authorship</p>