Hepatitis D (DELTA).

The hepatitis D virus (HDV) is unique in animal virology. It is the smallest of human pathogens, re- quires the HBsAg capsid of the hepatitis B virus (HBV) to assembly into infectious virions, and parasitizes the transcriptional machinery of the host. Hepatitis D is ubiquitous but prevalence varies throughout the world. It is the most severe form of chronic viral liver disorder. Vaccination against the HBV has decreased the circulation of HDV in industrialized countries but Hepatitis D remains a significant medical issue in many areas of the developing world.