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Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Oct 14, 2015; 21(38): 10811-10823
Published online Oct 14, 2015. doi: 10.3748/wjg.v21.i38.10811
Injecting drug use: A vector for the introduction of new hepatitis C virus genotypes
Simona Ruta, Costin Cernescu
Simona Ruta, Carol Davila University of Medicine and Pharmacy, Stefan S. Nicolau Institute of Virology, 030304 Bucharest, Romania
Costin Cernescu, Stefan S. Nicolau Institute of Virology, 030304 Bucharest, Romania
Author contributions: Ruta S and Cernescu C contributed equally to this work, designed the study, analyzed the data, and wrote the paper.
Supported by NIH grant 5P30 AI036211-19 (partially, subcontract PO 5600167489, through the Baylor International Pediatric AIDS Initiative); and the Romanian Academy Programme for the Stefan S. Nicolau Institute of Virology.
Conflict-of-interest statement: We undersigned, Simona Ruta and Costin Cernescu, authors of the review entitled “Injecting drug use: A vector for introduction of new hepatitis C virus genotypes”, submitted to World Journal of Gastroenterology declare no competing commercial, personal, political, intellectual, or religious interests in relation to the submitted work.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Simona Ruta, MD, PhD, Professor, Virology Chair, Carol Davila University of Medicine and Pharmacy, Stefan S. Nicolau Institute of Virology, 285 sos Mihai Bravu, 030304 Bucharest, Romania.
Telephone: +40-321-3242590 Fax: +40-213-241471
Received: April 27, 2015
Peer-review started: April 29, 2015
First decision: June 2, 2015
Revised: June 19, 2015
Accepted: September 15, 2015
Article in press: September 15, 2015
Published online: October 14, 2015

Hepatitis C virus (HCV) genotypes’ monitoring allows real-time insight into the dynamic changes that occur in the global epidemiological picture of HCV infection. Intravenous drug use is currently the primary driver for HCV transmission in developed and developing countries. The distribution of HCV genotypes/subtypes differs significantly between people who inject drugs (PWID) and the general population. HCV genotypes that previously exhibited a limited geographical distribution (3a, 4) are becoming more prevalent in this high-risk group. Immigration from HCV-endemic countries and the evolving networks of HCV transmission in PWID influence HCV genotypes distribution in Europe. Social vulnerabilities (e.g., unemployment, homelessness, and limited access to social and healthcare insurances systems) are important triggers for illicit drug use, which increases the associated risks of HCV infection and the frequent emergence of less prevalent genotypes. Genotype/subtype determination bears important clinical consequences in the progression of liver disease, susceptibility to antiviral therapies and the emergence of resistance-associated variants. An estimated half of the chronically HCV-infected PWID are unaware of their infection, and only one in ten of those diagnosed enter treatment. Nevertheless, PWID exhibit high response rates to new antiviral regimens, and the level of HCV reinfection is unexpectedly low. The focus of the healthcare system must be on the early detection and treatment of infection, to avoid late presentations that are associated with high levels of viremia and liver fibrosis, which may diminish the therapeutic success rate.

Keywords: Hepatitis C, Hepatitis C virus genotypes, Intravenous drug use, People who inject drugs, Direct-acting antivirals

Core tip: Careful surveillance of circulating hepatitis C virus (HCV) genotypes/subtypes is compulsory to reconstruct the natural history of HCV epidemics and viral transmission chains in high-risk populations, such as people who inject drugs (PWIDs). Genotypes 1a and 3a predominate among PWID worldwide, but genotype 4 has been reported with increased frequency. This review analyzes the factors that underlie the different distributions of HCV genotypes in PWID relative to the general population and highlights the need for early diagnosis and care in this vulnerable group, which responds well to new antiviral therapies and exhibits unexpectedly low reinfection rates.