Hepatitis D virus, also called delta virus, is a RNA virus which can replicate only in the presence of the hepatitis B virus. This is why it is impossible to have hepatitis D without having hepatitis B infection.
There are two types of hepatitis B+D infection: co-infection and super-infection. Co-infection is when both viruses B and D are inoculated at the same time – acute B+D hepatitis. Super-infection occurs when the individual already suffers from chronic hepatitis B and is infected with hepatitis D virus.
Most often hepatitis D virus is transmitted by blood contact (blood transfusions, parenteral drugs use, etc.), but can also be transmitted by sexual intercourse and from mother to child.