Hepatitis C virus (HCV) infects approximately 20-40% of the millions of incarcerated individuals in the United States. While many studies have characterized the seroincidence of chronic HCV infection, none have specifically addressed the issue of acute HCV infection. Since incarceration is associated with new onset intravenous drug use, such individuals would be at high risk for acute HCV infection. Screening of high-risk populations will shed insight into the incidence and clinical course of individuals and allow for characterization of their immune responses. Moreover, treatment outcomes for HCV are far better when treating early in infection, therefore identification of individuals with acute HCV is of extreme clinical benefit due to the greatly enhanced possibility of viral eradication. Interventions such as counseling, safe-needle techniques, and immunizations against hepatitis A and hepatitis B virus are also necessary. Without any systematic approach, preliminary efforts have identified 19 cases of acute HCV identified from 2 populations of incarcerated individuals over a 30-month period. This project aims to improve the identification of such subjects within the Massachusetts correctional system, describe their clinical courses, while providing access to counseling, education, and treatment for the identified individuals. Individuals identified in the correctional system uniquely complement the Brazilian cohort, since acute HCV associated with IVDU is not a frequent occurrence in our Brazilian patients. Moreover, we aim to analyze differences that explore the influence of race on the presentation of HCV. Therefore, the two cohorts will allow us to address the impact of risk factor for HCV acquisition on the immunology of acute HCV infection.