Hepatitis C virus infection epidemiology among people who inject drugs in Europe: a systematic review of data for scaling up treatment and prevention

Abstract

Background: People who inject drugs (PWID) are a key population affected by hepatitis C virus (HCV). Treatment options are improving and may enhance prevention; however access for PWID may be poor. The availability in the literature of information on seven main topic areas (incidence, chronicity, genotypes, HIV co-infection, diagnosis and treatment uptake, and burden of disease) to guide HCV treatment and prevention scale-up for PWID in the 27 countries of the European Union is systematically reviewed.

Methods and findings: We searched MEDLINE, EMBASE and Cochrane Library for publications between 1 January 2000 and 31 December 2012, with a search strategy of general keywords regarding viral hepatitis, substance abuse and geographic scope, as well as topic-specific keywords. Additional articles were found through structured email consultations with a large European expert network. Data availability was highly variable and important limitations existed in comparability and representativeness. Nine of 27 countries had data on HCV incidence among PWID, which was often high (2.7-66/100 person-years, median 13, Interquartile range (IQR) 8.7-28). Most common HCV genotypes were G1 and G3; however, G4 may be increasing, while the proportion of traditionally 'difficult to treat' genotypes (G1+G4) showed large variation (median 53, IQR 43-62). Twelve countries reported on HCV chronicity (median 72, IQR 64-81) and 22 on HIV prevalence in HCV-infected PWID (median 3.9%, IQR 0.2-28). Undiagnosed infection, assessed in five countries, was high (median 49%, IQR 38-64), while of those diagnosed, the proportion entering treatment was low (median 9.5%, IQR 3.5-15). Burden of disease, where assessed, was high and will rise in the next decade.

Conclusion: Key data on HCV epidemiology, care and disease burden among PWID in Europe are sparse but suggest many undiagnosed infections and poor treatment uptake. Stronger efforts are needed to improve data availability to guide an increase in HCV treatment among PWID.

Conflict of interest statement

Competing Interests: Maria Emília Resende (MER) is an employee of Merck Sharp & Dohme and is a member of the EMCDDA DRID Group. MER provided support to Mário Martins, Domingos Duran and Graça Vilar, who are members of the EMCDDA DRID Group, in identifying studies on viral hepatitis in Portugal, but has not been involved in any way with the setting up, writing up of, or commenting on the study. There are no patents, products in development or marketed products to declare. This does not alter the authors’ adherence to all the PLOS ONE policies on sharing data and materials.

Figures

Figure 1. Flow diagram of study selection aggregated over the seven topic areas reviewed.

Figure 2. Incidence of HCV infection in PWID (per 100 person years).

Figure 3. Chronicity of HCV: RNA prevalence (%) among antibody-positive PWID.

Figure 4. Proportion (%) of HCV infections among PWID that are genotypes 1 or 4.

Figure 5. Proportion (%) of HCV-infected PWID that are co-infected with HIV.

Figure 6. Proportion (%) of HCV positive PWID (antibody or RNA) undiagnosed.

Figure 7. Proportion (%) of HCV-infected PWID entering antiviral treatment in observational studies in non-clinical settings.

Figure 8. HCV antibody prevalence (%) among PWID injecting

Note Figure 8: Source EMCDDA, 2013. (http://www.emcdda.europa.eu/stats13#inf:displayTables); black squares are data with national coverage, blue triangles are data with sub-national (local, regional) coverage.

Figure 9. HCV antibody prevalence (%) among PWID in the EU, 2006–2011.

Note Figure 9: Source EMCDDA, 2013 (http://www.emcdda.europa.eu/stats13#inf:displayTables); black squares are data with national coverage, blue triangles are data with sub-national (local, regional) coverage.