title: 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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors: European Monitoring Centre for Drugs and Drug Addiction (EMCDDA), Lisbon, Portugal.
authors: Lucas
authors: L
authors: Wiessing
authors: European Monitoring Centre for Drugs and Drug Addiction (EMCDDA), Lisbon, Portugal.
authors: Marica
authors: M
authors: Ferri
authors: Cluster Infectious Diseases, Department of Research, Public Health Service, Amsterdam, The Netherlands; Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, Amsterdam, The Netherlands.
authors: Bart
authors: B
authors: Grady
authors: National Reference Centre for Retroviruses, Laboratory of Hygiene, Epidemiology and Medical Statistics, University of Athens Medical School, Athens, Greece.
authors: Maria
authors: M
authors: Kantzanou
authors: Copenhagen HIV Programme (CHIP), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors: Ida
authors: I
authors: Sperle
authors: HIV & STI Department, Centre for Infectious Disease Surveillance and Control, Public Health England, London, United Kingdom.
authors: Katelyn J
authors: KJ
authors: Cullen
authors: National Reference Centre for Retroviruses, Laboratory of Hygiene, Epidemiology and Medical Statistics, University of Athens Medical School, Athens, Greece.
authors: Angelos
authors: A
authors: Hatzakis
authors: Cluster Infectious Diseases, Department of Research, Public Health Service, Amsterdam, The Netherlands; Center for Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, Amsterdam, The Netherlands.
authors: Maria
authors: M
authors: Prins
authors: London School of Hygiene and Tropical Medicine (LSHTM), London, United Kingdom; School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom.
authors: Peter
authors: P
authors: Vickerman
authors: Copenhagen HIV Programme (CHIP), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors: Jeffrey V
authors: JV
authors: Lazarus
authors: HIV & STI Department, Centre for Infectious Disease Surveillance and Control, Public Health England, London, United Kingdom; London School of Hygiene and Tropical Medicine (LSHTM), London, United Kingdom.
authors: Vivian D
authors: VD
authors: Hope
authors: Department of Public Health and Primary Care, KULeuven, Leuven, Belgium.
authors: Catharina
authors: C
authors: Matheï
mesh_terms: D015897:Comorbidity; D005060:Europe / Q000453:epidemiology; D005062:European Union / Q000706:statistics & numerical data; D015658:HIV Infections / Q000453:epidemiology; D006526:Hepatitis C / Q000188:drug therapy / Q000453:epidemiology* / Q000517:prevention & control; D006801:Humans; D015994:Incidence; D015995:Prevalence; D015819:Substance Abuse, Intravenous / Q000453:epidemiology*