While the risk of hepatitis C virus (HCV) infection is high among people who use drugs (PWUD), screening and treatment for chronic hepatitis C remain limited in this population. The objective of this study is to assess the health impact of the network of medical microstructures on the screening, monitoring, and treatment of patients with substance use disorders who are registered with these facilities. In partnership with the "Viral Hepatitis" Reference Center at the University Hospitals of Strasbourg, the "RMS Alsace" network of medical microstructures followed 526 PWID and 111 non-at-risk patients over a two-year period. HCV screening, performed on 80% of IDUs, showed that 39% of them were seropositive compared to 4.5% among non-at-risk patients (p<0.001). The seropositivity rate among IDUs varied with age: 7% of those under 30 vs. 80% of those over 45 were infected. Furthermore, injection use was most common among older individuals. Those under 30 appeared to be switching to snorting. In 88% of cases, serology was supplemented by HCV RNA testing. Therapeutic management was initiated in 43 patients, representing 40% of HCV-RNA-positive patients. These results, which are more favorable than those reported in the literature, demonstrate that the networked system of medical microstructures has a positive public health impact on the screening, monitoring, and treatment of hepatitis C among patients receiving care within this system. (R.A.)