Hepatitis D is an acute inflammation of the liver brought on by Hepatitis D virus (HDV): a “defective” virus that requires the simultaneous presence of hepatitis B virus (HBV) in order to infect liver cells, multiply and cause disease.
HDV is prevalent in several countries, but generally confined to specific population subgroups also affected by acute or chronic HBV infection (in particular, drug users).
Co-infection by HDV and HBV can cause particularly severe (even fulminant) forms of acute hepatitis, while super-infection by HDV in a person with chronic hepatitis B can reactivate the B virus in latent form and cause severe flare-ups of the disease.
