What Makes Hepatitis Unique? Liver Tropism, Transmission Routes, and Chronic Infection

Hepatitis viruses (A–E) are defined by their hepatotropism and diverse epidemiology.

Defining Features

1. Liver-Specific Tropism: Receptors (e.g., NTCP for HBV/HDV, SR-BI/CD81 for HCV) restrict replication to hepatocytes → primary hepatic pathology.
2. Multiple Transmission Routes:
   • Blood-borne: HBV, HCV, HDV (needles, transfusion, perinatal)
   • Sexual: HBV, HCV (less efficient)
   • Fecal-oral: HAV, HEV (contaminated water/food)
3. Chronicity & Carrier State: HBV (5–10% adults), HCV (70–85%) establish persistent infection → cirrhosis, HCC. HAV/HEV typically acute.
4. Clinical Spectrum: Asymptomatic → acute icteric hepatitis → fulminant hepatic failure → chronic hepatitis → cirrhosis → HCC.
5. Prevention & Cure: Vaccines for HAV, HBV (also prevents HDV). Direct-acting antivirals cure >95% HCV. HBV suppressed with nucleos(t)ide analogs.

Public Health Impact

354 million people living with chronic HBV/HCV (WHO 2024). Vaccination, harm reduction, screening, and treatment access are elimination pillars.