Define Hepatitis B. Describe its prevention and management.

Definition

• Hepatitis B is caused by the hepatitis B virus (HBV), a DNA virus transmitted parenterally, sexually and vertically (mother-to-child).
• Vertical and early-childhood transmission are the major routes in high-prevalence regions like India.

Natural History

• Acute infection is often subclinical in children.
• The younger the age at infection, the higher the risk of chronic carriage — up to 90% in perinatally infected infants.
• Chronic HBV can progress to cirrhosis and hepatocellular carcinoma.

Serological Markers

Prevention (the Key Focus)

• Hepatitis B vaccine — a birth dose within 24 hours plus the primary series (part of the pentavalent vaccine in India's UIP).
• HBIG + vaccine at birth for babies of HBsAg-positive mothers.
• Safe blood, sterile needles, and screening of blood donors and pregnant women.

Management

• Acute hepatitis B — supportive care (as for viral hepatitis).
• Chronic hepatitis B — antiviral therapy (e.g. Tenofovir/entecavir) in selected children, with specialist follow-up and HCC surveillance.

Interpreting Common Patterns

• HBsAg positive > 6 months = chronic infection.
• HBsAg negative + anti-HBs positive = immunity (vaccination or past infection).
• HBeAg / high HBV-DNA = high infectivity and active replication.

Public-health Importance

Because perinatal and early-childhood infection carries the highest chronicity, the birth-dose vaccine and antenatal screening are the most effective tools to reduce the future burden of cirrhosis and liver cancer.

Phases of Chronic HBV

• Immune-tolerant — HBeAg+, high HBV-DNA, normal ALT (common after perinatal infection).
• Immune-active — raised ALT, liver damage (treatment considered).
• Inactive carrier — HBeAg−, low DNA, normal ALT; resolution — anti-HBs+.

Birth dose within 24 hours prevents vertical transmission.