Hepatitis Basics

Viral hepatitis encompasses five major viruses (A through E) with distinct transmission routes, clinical courses, and management strategies. Hepatitis A (HAV) and E (HEV) are transmitted fecal-orally and cause self-limited acute hepatitis without chronic progression (mnemonic: vowels = bowel). Hepatitis B (HBV), C (HCV), and D (HDV) are blood-borne and can cause chronic hepatitis leading to cirrhosis and hepatocellular carcinoma (mnemonic: consonants = blood/body fluids). HBV is unique as the only DNA hepatitis virus (all others are RNA). HBV serology is complex but systematic: HBsAg indicates active infection (acute or chronic); anti-HBs indicates immunity (vaccine or resolved infection); IgM anti-HBc indicates acute infection; total anti-HBc indicates any prior exposure; HBeAg indicates high viral replication and infectivity. The 'window period' occurs when HBsAg has cleared but anti-HBs has not yet appeared — only IgM anti-HBc is positive during this period. HCV has no protective antibody; anti-HCV indicates exposure but requires HCV RNA quantification to confirm active infection (anti-HCV remains positive after cure). HCV is now curable with direct-acting antivirals (DAAs) achieving >95% sustained virologic response (SVR) in 8-12 weeks. HBV is...