Hepatitis types B and non-B. Epidemiologic background.

Two episodes of acute viral hepatitis occurred in each of 34 patients. One episode in each patient was serologically diagnosable as type B hepatitis on the basis of tests for hepatitis B surface antigen or antibody. The other episode was classified as "non-B" on the basis of seronegativity, reinforced by seropositivity in an alternate bout. An epidemiologic background appropriate to "serum" hepatitis, either transfusion (one bout) or illicit self-injection (46 bouts), was associated just as frequently with serologically non-B episodes as with identified type B disease. The diagnosis of type B hepatitis, therefore, should be made only on the basis of serologic tests specific for hepatitis B virus infection. Other cases of sporadic diseases in adults must be labeled "viral hepatitis, type unspecifiable."