HBsAg is a protein that appears in blood during hepatitis B infection. It's part of the virus's outer layer protecting it from immune system. HBsAg levels range from 0.05 to 250 IU/ml
Endemic diseases are consistently present but limited to a specific region. Prevalence is measured by dividing cases by total population over time. Endemic diseases can be rare or high in prevalence
Hepatitis B is a liver infection caused by the HBV virus. Acute infection lasts less than 6 months, chronic lasts 6 months or more. Symptoms typically appear 1-4 months after infection. Common symptoms include abdominal pain, dark urine, fever, and jaundice
HCC is the most common primary liver cancer in adults. Most cases occur in people with chronic liver disease, especially cirrhosis. Hepatitis B causes about 50% of HCC cases, hepatitis C about 25%. Disease is three times more common in males than females
Epidemic is rapid spread of disease to large population within short time. Meningococcal epidemic requires 15 cases/100,000 for two consecutive weeks
Hepatitis B vaccine prevents hepatitis B infection. First dose recommended within 24 hours of birth. Routine immunization protects over 95% of healthy people. Safe during pregnancy and breastfeeding