Delta hepatitis only occurs in patients who also have either acute or chronic infection with hepatitis B virus. The delta agent is

The delta agent was first described in 1977 and has recently been shown to be an incomplete RNA virus that requires HBsAg for replication. It is found most often in persons who have multiple parenteral exposures, for example, intravenous (IV) drug abusers, hemophiliacs, and multiply transfused patients.