The circulation of the Hepatitis D Virus (HDV) has considerably diminished in Italy, secondary to the control of the Hepatitis B Virus (HBV) with vaccination; this has led to the perception that HDV is vanishing and has reduced attention to the diagnosis of Hepatitis D. However, migratory fluxes from HDV endemic areas, fostered by labour-forces globalization, are increasingly reconstituting the reservoir of HDV in the country and hepatitis D has not yet vanished in native Italians but will remain an important medical issue for several years to come. As the epidemiologic and clinical features of HDV infection in migrant communities are largely unknown and the features of native Italians with long standing HDV infections have not been updated, this project intends to establish the contemporary epidemiological and medical context of HDV in immigrants in Italy and to determine the clinical characteristics and needs of the residual cohort of native HDV Italians, through the analysis of all HDV cases recruited in 12 months in a coordinated network of 35 Italian medical centers. The data will provide an appraisal of the burden of hepatitis D in the country and of its impact on the National Health System. They will present the paradigm of the current trend of HDV infection in high-income countries in the world.

Inclusion Criteria:

• HBsAg-positive subjects
• 18 years or older
• anti-HD-positive

Patients will be recruited in a Country-wide coordinated network of national medical centers. The network will include hepatology, infectious disease and internal medicine centers that historically care for patients with viral liver disease, located in the 12 major regions of Italy.