A blood donor tests HBsAg-positive but feels fine — chronic hepatitis B carrier. HBsAg persisting >6 months means chronic infection — often asymptomatic for decades while silently scarring the liver toward cirrhosis and cancer. Family screened and vaccinated; the carrier monitored (LFT, viral load, ultrasound) and treated (tenofovir/entecavir) if active. Blood-bank screening catches these — one positive bag protects dozens. The silent carrier is hepatitis B's strategy — find them before the liver fails.