Clinical meaning
Viral hepatitis involves inflammation and necrosis of hepatocytes caused by hepatotropic viruses (A through E). Hepatitis A (HAV) and E (HEV) are transmitted via the fecal-oral route and cause acute, self-limiting infections. HAV enters enterocytes, reaches the liver via portal circulation, and replicates in hepatocytes; the immune response (cytotoxic T cells) causes hepatocyte destruction rather than the virus itself. Hepatitis B (HBV) is a DNA virus transmitted through blood, sexual contact, and vertical transmission; it integrates into the host genome and can cause chronic infection. HBV surface antigen (HBsAg) persistence >6 months defines chronic HBV, which carries risk for cirrhosis and hepatocellular carcinoma. Hepatitis C (HCV) is an RNA virus transmitted primarily through blood; it evades immune clearance through rapid mutation, causing chronic infection in 75-85% of cases. Chronic HCV drives progressive fibrosis through persistent inflammation and stellate cell activation. Hepatitis D (HDV) is a defective RNA virus requiring HBV coinfection to replicate. All forms produce elevated aminotransferases (ALT > AST in viral hepatitis, unlike alcoholic liver disease where AST > ALT), conjugated hyperbilirubinemia, and potential coagulopathy.