Hepatitis B: Transmission, Serology and Treatment

Hepatitis B is a viral infection of the liver caused by the hepatitis B virus (HBV), a DNA virus. It can cause acute hepatitis and lifelong chronic infection leading to cirrhosis and liver cancer. It is preventable by vaccination, and chronic infection can be controlled with antiviral medicines.

Transmission

• Mother to baby at birth (vertical) — the most common route in high-prevalence regions.
• Blood — unsafe injections, reused needles or syringes, unscreened blood transfusion, and sharing razors or toothbrushes.
• Sexual contact.
• Needlestick injuries in health workers.

The younger a person is when infected, the more likely the infection is to become chronic. Most infected newborns develop chronic infection, compared with a small minority of infected adults.

Clinical features

Acute hepatitis B may cause no symptoms, or:

• fatigue and loss of appetite
• nausea
• right upper abdominal pain
• jaundice, dark urine and pale stools

Rarely, it causes acute liver failure.

Chronic hepatitis B is often silent for years until cirrhosis or liver cancer develops.

Understanding the blood tests

• HBsAg (surface antigen) — current infection. If present for more than 6 months, the infection is chronic.
• Anti-HBs (surface antibody) — immunity, from vaccination or recovery.
• Anti-HBc (core antibody) — past or current infection; never produced by vaccination. IgM anti-HBc suggests acute infection.
• HBeAg — usually a marker of high viral replication and infectivity.
• HBV DNA (viral load) — guides treatment decisions.

Typical patterns:

• Vaccinated: anti-HBs only.
• Past infection, recovered: anti-HBc and anti-HBs.
• Chronic infection: HBsAg and anti-HBc (IgG) for more than 6 months.

Assessment of chronic infection

• Liver function tests, especially ALT.
• HBV DNA.
• HBeAg status.
• Assessment of liver fibrosis, for example by elastography.
• Ultrasound.
• Tests for coinfection with hepatitis D (delta), hepatitis C and HIV.
• Hepatitis A immunity.

Treatment

• Acute hepatitis B: mainly supportive. Specialist care if the liver is failing.
• Chronic hepatitis B: treatment decisions depend on viral load, ALT, fibrosis and other factors, and guidelines are broadening who should be treated. First-line drugs are the nucleos(t)ide analogues tenofovir or entecavir, usually taken long term. They suppress the virus and reduce the risk of cirrhosis and cancer, but rarely cure the infection completely. Pegylated interferon is used in selected patients.
• Surveillance: patients at risk, especially those with cirrhosis, need ultrasound (with or without alpha-fetoprotein) about every 6 months to detect hepatocellular carcinoma early.

Prevention

• Vaccination, including a birth dose within 24 hours of birth, followed by the routine infant series.
• Babies of HBsAg-positive mothers need vaccine plus hepatitis B immunoglobulin at birth. Mothers with high viral loads may receive antiviral treatment in late pregnancy.
• Safe injections, screening of blood, and safe sex.
• Vaccination of health workers, with checking of their antibody response.
• Post-exposure prophylaxis after needlestick injuries.

Exam pearls

• Anti-HBc separates natural infection from vaccination.
• HBsAg positive for more than 6 months means chronic infection.
• Hepatitis B can cause liver cancer even without cirrhosis.

See also Hepatitis C, Liver Cirrhosis and the hepatology part of the Medicine Companion.

Test yourself

5 exam-style single-best-answer questions. Choose your answer, then tap “Show answer”.

1. HBsAg negative, anti-HBs positive, anti-HBc negative. Interpretation?

   1. Immunity from vaccination
   2. Chronic infection
   3. Window period
   4. Acute infection
   5. Past infection
   Show answer

   Answer: A. Immunity from vaccination
   Anti-HBs alone indicates vaccine-induced immunity; natural infection produces anti-HBc.

2. HBsAg positive for more than 6 months means:

   1. Chronic hepatitis B
   2. False positive
   3. Hepatitis A
   4. Recovery
   5. Vaccination
   Show answer

   Answer: A. Chronic hepatitis B
   Persistence of HBsAg beyond 6 months defines chronic infection.

3. Which marker suggests acute hepatitis B?

   1. Anti-HBs
   2. Anti-HBe
   3. IgG anti-HBc
   4. IgM anti-HBc
   5. HBV genotype
   Show answer

   Answer: D. IgM anti-HBc
   IgM anti-HBc indicates recent (acute) infection.

4. When should the first dose of hepatitis B vaccine be given to newborns?

   1. Within 24 hours of birth
   2. Only if mother is positive
   3. At 9 months
   4. At school entry
   5. At 6 weeks
   Show answer

   Answer: A. Within 24 hours of birth
   WHO recommends a birth dose within 24 hours for all infants.

5. Which drug is first-line for chronic hepatitis B?

   1. Oseltamivir
   2. Sofosbuvir
   3. Tenofovir
   4. Aciclovir
   5. Ribavirin
   Show answer

   Answer: C. Tenofovir
   Tenofovir and entecavir are first-line nucleos(t)ide analogues.

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Disclaimer

For education and exam preparation only. This is not medical advice and must not be used to diagnose or treat patients. Always follow current clinical guidelines and the advice of qualified senior colleagues.