Non-A, Non-B Hepatitis Virus Infection

Occurrence of cases of post-transfusion hepatitis without serological evidence of either hepatitis B or A infection led to the recognition of `non-A, non-B' hepatitis. At least two distinct viruses are involved. In industrialized countries approximately 90% of cases of post-transfusion hepatitis are caused by the hepatitis C virus, an RNA virus which may be related to the arthropod-borne encephalitis viruses. Approximately 150,000 cases of hepatitis C infection occur in the United States every year. Only 5-10% are associated with blood transfusions; about 40% are associated with intravenous drug use, and 10% occur in heterosexual individuals with multiple sexual partners or household or sexual contacts of a patient with hepatitis. No source of infection can be identified in 40% of cases. Chronic liver disease develops in approximately 50% of individuals infected with the hepatitis C virus, and both cirrhosis and hepatocellular carcinoma are common sequelae. In recent studies approximately one-half of patients with chronic hepatitis C responded to administration of alpha interferon, but relapse was frequent after discontinuation of therapy. Corticosteroids are ineffective in the treatment of chronic hepatitis C infection.

Epidemics of water-borne hepatitis in less developed countries have been linked to an immunologically distinct virus, designated hepatitis E virus. This small RNA virus is present in the faeces of infected individuals, and has been demonstrated in the hepatocytes of experimentally-infected cynomolgus macaque monkeys. Hepatitis E virus appears to be one of the most common causes of acute hepatitis and jaundice in the Third World, but is rare in the United States.

The clinical illness produced by the hepatitis C and E viruses is usually mild, but there is a high case fatality rate in pregnant women who become infected with hepatitis E virus. Transient improvement followed by relapse is commonly seen in infection with hepatitis C virus The histopathological features are not always distinctive, but in some cases there is a disproportionate sinusoidal infiltrate and fat may be present . Chronic hepatitis, which commonly follows infection with hepatitis C virus, is not seen in association with water-borne infections due to hepatitis E virus.