Long-incubation (virus B, HAA-associated) hepatitis.

Virus B hepatitis is differentiated from virus A hepatitis by the presence ofAustralia antigen in the serum. This most interesting antigen was discovered incidentally. In 1965, Blumberg, a geneticist, and his colleagues were working in Philadelphia on the development of antibodies against human serum lipoproteins in multiply transfused subjects. They found that in two haemo- philic patients there was an antibody which reacted with an antigen in a single serum in their panel and this came from an Australian Aborigine'. The antibody, an immunoglobulin G, was found in many patients who had been multiply transfused. Later it was detected in some 20 % of patients with viral hepatitis. Because of its discovery in an Aboriginal serum, the antigen was called Australia antigen. The more general term, hepatitis-associated antigen (HAA), is also employed. The antigen is present in about 82 % of sera from patients suffering from long-incubation hepatitis if tested within 12 days of the onset of symptoms. It is usually cleared from the serum by three to four weeks. Patients transfused with blood containing the antigen will either develop icteric or anicteric hepatitis or will remain asymptomatic2.