RESEARCH Open Access New hepatitis C virus infection, re-infection and associated risk behaviour in male Irish prisoners: a cohort study, 2019 Des Crowley 1,2* , Gordana Avramovic 1 , Walter Cullen 1 , Collette Farrell 2 , Anne Halpin 2 , Mary Keevans 2 , Eamon Laird 3 , Tina McHugh 4 , Susan McKiernan 5 , Sarah Jayne Miggin 6 , Ross Murtagh 1 , Eileen O. Connor 6 , Marie O’Meara 7 , Deirdre O. Reilly 2 and John S. Lambert 1,4 Abstract Background: Prisoners are recognised as a high-risk population and prisons as high-risk locations for the transmission of hepatitis c virus (HCV) infection. Injecting drug use (IDU) is the main driver of HCV infection in prisoners and harm reduction services are often suboptimal in prison settings. HCV prevalence and incident data in prisoners is incomplete which impacts the public health opportunity that incarceration provides in identifying, treating and preventing HCV infection. The aim of this study is to identify new HCV infection and associated risk factors in an Irish male prison. Methods: We conducted a follow up (18-month) cohort study on prisoners who had previously tested negative, self- cleared or had been successfully treated for HCV infection. We conducted the study in a male medium security prison located in Dublin Ireland (Mountjoy Prison) using HCV serology, a review of medical records and a researcher- administered questionnaire. Results: 99 prisoners with a mean age of 33.2 yrs. participated in the study and 82(82.8%) completed a research- administered questionnaire. Over half (51%) had a history of drug use from a young age (14.8 yrs.), 49.9% a history of heroin use and 39% a history of IDU. The prevalence of HIV and hepatitis B virus core antibody was 3% and HCV antibody was 22.2%. No new HCV infections were identified in those who had never been infected (n = 77), had self- cleared (n = 9) or achieved sustained virological response (n = 12). Small numbers of prisoners continued to engage in risk-behaviour including, IDU both in the prison (n = 2) and the community (n = 3), sharing syringes (n = 1) and drug taking paraphernalia (n = 6) and receiving non-sterile tattoos (n= 3). Conclusion: Despite the high numbers of Irish prisoners with a history of IDU and HCV infection, new HCV infection is low or non-existent in this population. Small numbers of prisoners continue to engage in risk behaviour and larger studies are required to further understand HCV transmission in this cohort in an Irish and international context. Keywords: Hepatitis C, HCV, Prisoner, Prison, Incident, Harm reduction, Medication assisted treatment, MAT © The Author(s). 2021 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. * Correspondence: doctordes@hotmail.com 1 School of Medicine, University College Dublin, Dublin, Ireland 2 Irish Prison Service, Dublin, Ireland Full list of author information is available at the end of the article Crowley et al. Archives of Public Health (2021) 79:97 https://doi.org/10.1186/s13690-021-00623-2