Current nomenclature, viral agents, and clinical aspects of hepatitis C and hepatitis E

Abstract

Hepatitis C and hepatitis E (Non-A, Non-B hepatitis-NANBH) are important transmissible diseases whose precise causative agents and diagnosis remain not entirely resolved problems, despite of recent progress. It was first identified as a type of blood-transfusion-associated hepatitis which on serological testing, was unrelated to hepatitis A or hepatitis B infection (Feinstone et al., 1975). In the 1970’s during the clinical recognition and description of cases of post-transfusion hepatitis, NANBH, the long incubation hepatitis was noted for its mild, often subclinical presentation but high rates of chronicity and progression to cirrhosis. A similar illness could also be transmitted by blood products such as clotting factors (Dienstag, 1983a). An important series of studies in chimpanzees clearly showed the presence of a transmissible agent in blood products and in serum from carrier blood donors (Dienstag, 1983b). The agent was characterized as being sensitive to organic solvents. Even in the absence of conventional virological studies in vitro or knowledge of the genome, it was possible for Bradley (1985a, b) to make a calculated guess that the NANBH agent could be a small togavirus-like enveloped RNA virus. Presently, the agent of parentally transmitted non-A, non-B hepatitis is known as hepatitis C virus (Choo et al., 1989; Houghton et al., 1991). The recent studies of hepatitis C virus genome revealed three types of HCV distantly related (Takayasu et al., 1992; Chan et al., 1992) and Cha et al. (1992) demonstrated five related but distinct HCV genotypes.