Chronic hepatitis C virus (HCV) infection is the second leading cause of primary liver cancer worldwide and the leading cause in the United States. In 2020, an estimate 260,000 deaths were attributable to HCV globally, nearly 80,000 of which occurred in Europe, mainly due to complications such as cirrhosis or hepatocellular carcinoma (HCC).

The CARTO-VHC study is a retrospective, observational, multicenter study based on data and samples collected during routine care from 2023 to 2024. The study does not involve direct human participation. The study aims to describe the different genotypes and subtypes of the hepatitis C virus, including unusual subtypes, in a large population of newly diagnosed HCV-positive patients. This will help identify the most common types circulating in France. Additionally, the study will provide a comprehensive understanding of therapeutic failures and drug resistance to direct-acting antivirals (DAA) in treated patients.

The study will consist of the following:

1. Inclusion of patients who meet the selection criteria (hospitalized patients and outpatients from tertiary centers in mainland France) ;
2. Collecting all associated data, including demographic, clinical, and therapeutic information. A Clinical research technician may be assigned to centers lacking sufficient human resources;
3. Collect leftover patient specimens for viral genotyping (phylogenetic analysis of a portion of the NS5B gene, the reference method) or complete genome sequencing of unusual subtypes;
4. Perform molecular biology genotyping techniques (RNA extraction, PCR, and Sanger sequencing of a portion of the NS5B gene);
5. Carry out next-generation sequencing (Seq2000, Illumina) of the full genome of "unusual" subtype strains, or DAAs resistant patients
6. Analyze genotype and subtype information, as well as its correlation with demographic, clinical, and therapeutic data.

Inclusion Criteria:

• Patient aged 18 years old or more
• Newly diagnosed patient positive for HCV (presence of HCV antibodies)
• Patient with active infection (HCV RNA > 0)

Exclusion Criteria:

• Patients who decline to participate in the study and oppose the use of their personal data
• Patients under legal protection (guardianship or curatorship)

Defined population