Hepatitis D is caused by Hepatitis D virus (Delta agent) - a defective (36 nm-43 nm) enveloped RNA virus, which requires co-infection with Hepatitis B virus (HBV) for its replication. Transmitted sexually or percutaneously through contact with infected blood or blood products., HDV is associated with the most severe forms of chronic and acute hepatitis in many Hepatitis B -HBsAg positive patients. Since the infection with HDV requires infection with HBV, the development of the disease depends on whether the two viruses infect simultaneously (coinfection) or whether the newly infected HDV patient is also a chronic HBV carrier (superinfection).
The co-infection with HDV can lead to severe acute hepatitis disease with low risk of chronic stage development. Chronic HBV carrier patients superinfected with HDV are at risk to develop chronic HDV disease, which can lead to cirrhosis in 70%-80% of the patients. The serological diagnosis of HDV is based on detection of specific HDV antibodies (anti-HDV) or antigens.