National Cohort of Patients Co-infected With Hepatitis B and Delta Viruses

This is a multicentre observational study with prospective and retrospective data collection and retrospective data collection and biological collection from patients with HBV/HDV co-infection.

This is an observatory for patients co-infected with hepatitis B and Delta viruses. Patients will be monitored according to the usual recommendations, depending on their status: * Patients who have never received specific treatment for hepatitis Delta (untreated or receiving treatment with peginterferon alpha 2a alone) will be monitored according to current recommendations, once every 6 months; * Patients treated or having been treated with a specific hepatitis Delta treatment will be monitored according to the compassionate access protocol or according to the recommendations of the AMM during treatment and according to routine follow-up after the end of treatment. Participation in research entails the following additional procedures for patients, for each line of treatment, where applicable: * Samples for the biobank, * Self-administered questionnaires. In addition, as sub-studies are planned on sub-groups of patients, these sub-studies may involve additional constraints/interventions