Study of an epidemic of non-A, non-B hepatitis. Possibility of another human hepatitis virus distinct from post-transfusion non-A, non-B type.

A common source waterborne epidemic of viral hepatitis was studied in Kashmir valley over the six month period from November 1978 to April 1979. Highly sensitive serologic tests for hepatitis B and hepatitis A failed to reveal either one as an etiologic agent of hepatitis. Of 16620 inhabitants of the area screened four times in these six months, viral hepatitis developed in 1.65 per cent. In addition, 27.3 per cent of 128 persons who had contacts with patients who had viral hepatitis had biochemical features of anicteric hepatitis. The mode of spread of the epidemic, length of incubation, clinical features and biochemical test results of the patients studied resembled that of hepatitis A. These findings were in contrast to that of non-A, non-B hepatitis following transfusion, which closely resembles hepatitis B. The data strongly suggest the possibility of another human hepatitis virus and established the fecal oral route of its spread.