Sensitive serologic tests capable of diagnosing essentially all infections with hepatitis A virus and hepatitis B virus (HBV) have shown that certain patients with a viral hepatitis-like syndrome have neither hepatitis A nor hepatitis B. Such cases of non-A, non-B hepatitis have been most frequently recognized in studies of transfusion-associated hepatitis. Less than 20% of posttransfusion hepatitis is due to HBV if only blood from voluntary donors that has been screened by thirdgeneration tests for the presence of hepatitis B surface antigen is used for transfusion. Type A hepatitis rarely, if ever, results from blood transfusion.1,2 Thus, most transfusion-associated hepatitis in the United States has an unknown cause.
Non-A, non-B hepatitis resembles type B disease in several respects. First, the common route of infection by blood or blood products indicates that a chronic carrier state must exist in relatively asymptomatic persons. Second, non-A, non-B hepatitis has been found to