Primary viral infection of liver cells is caused by several distinct hepatotropic viruses transmitted by oral and parenteral routes. While the clinical, epidemiological, pathological, and immunological aspects of viral hepatitides have many common attributes and subtle differences (39), the etiologies of liver disorders cannot be established on the basis of clinical signs and symptoms or abnormal liver function tests (e.g., elevated alanine aminotransferase [ALT]). Following the discovery of Australia antigen (8), which was subsequently termed hepatitis B surface antigen (HBsAg), the identification and characterization of hepatitis B virus (HBV), hepatitis A virus (HAV),