Incidence of hepatitis C among people who inject drugs in Ireland
by Sean Millar

Hepatitis C is an infection of the liver caused by the hepatitis C virus (HCV). The acute phase of the infection is usually asymptomatic, but approximately 75% of those infected develop chronic infection, which may cause liver cirrhosis, hepatocellular carcinoma and liver failure.1,2 Injecting drug use is one of the main modes of transmission of HCV infection in Ireland. However, comprehensive information on the incidence and duration of HCV infection among people who inject drugs (PWID) in Ireland is lacking.


Recent research examined the incidence of HCV infection among PWID in the Republic of Ireland over a 13-year period. In this study, which was published in the BioMed Central (BMC) journal Hepatology, Medicine and Policy,3 anonymised data from the National Drug Treatment Reporting System (NDTRS) were used to identify all PWID who entered drug treatment for the first time between 1991 and 2014. A curve, estimating the incidence of injecting, was created in order to plot PWID by year of commencing injecting. The curve was adjusted for missing data on PWID in treatment, and for injectors who were never treated. Additional adjustment was made to account for PWID who had never shared injecting equipment. The incidence of HCV infection and chronic HCV infection among PWID was estimated by applying published rates.


It was found that between 1991 and 2014, 14 320 injectors were registered with the NDTRS. The majority were young (median age 25 years), male (74%), lived in Dublin (73%), and injected an opiate (94%). The estimated total number of injectors up to the end of 2014 was 16 382. The authors estimated that 12 423 (95% CI: 10 799‒13 161) individuals were infected with HCV, and that 9317 (95% CI: 8022‒9966) of these subjects became chronically infected. The estimated annual number of new HCV infections among PWID drugs peaked in 1998 (Figure 1). By 2014, almost 30% of injectors were estimated to have been infected for over 20 years.


Research has indicated that the prevalence of opiate use in Ireland may have stabilised,4 and that the number of PWID entering drug treatment for the first time in Ireland has decreased slightly in recent years.5 Nevertheless, injecting drug use remains a significant issue. As the EMCDDA recommend the collection of accurate data on the incidence of injectors entering drug treatment,6 the study authors concluded that the analysis demonstrates the wider usefulness of routine drug treatment data collected by the NDTRS. This may help inform policy with regard to the use of highly effective but expensive new treatments for HCV that have recently become available.




1    World Health Organization (2014) Guidelines for the screening, care and treatment of persons with hepatitis C infection. Geneva: World Health Organization.

2    Global Burden of Hepatitis C Working Group (2004) Global burden of disease (GBD) for hepatitis C. Journal of Clinical Pharmacology, 44: 20‒29.

3    Carew AM, Murphy N, Long J, Hunter K, Lyons S, Walsh C and Thornton L (2017) Incidence of hepatitis C among people who inject drugs in Ireland. Hepatology, Medicine and Policy, 2: 7.

4    Hay G, Jaddoa A, Oyston J and Webster J (2017) Estimating the prevalence of problematic opiate use in Ireland using indirect statistical methods. Dublin: National Advisory Committee on Drugs and Alcohol. [AW1]  (Forthcoming)

5    European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) (2011) Statistical bulletin. Treatment demand indicator (TDI). Lisbon: EMCDDA.

6    European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) (2013) PDU (Problem drug use) revision summary. Lisbon: EMCDDA.


Figure 1                Estimates of new injectors by year commenced injecting and new HCV infections by year infected

                        Source: Carew AM, Murphy N, Long J, Hunter K, Lyons S, Walsh C and Thornton L, 2017


 [AW1]Is a digital version available?