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Hepatitis B

Hepatitis B

2 December 2022

Causative agent

Hepatitis B infection is caused by hepatitis B virus (HBV).

Clinical features

The virus can cause acute hepatitis. Fewer than 5% of infected children under 5 years of age and 30-60% of infected adults are symptomatic. Common presentations include fever, loss of appetite, nausea, vomiting, abdominal pain, yellow coloring of the eyes, dark urine and clay colored or light stools. Symptomatic or not, approximately 5-10% of adults and 95% of perinatally infected infants are unable to clear the virus, thus becoming chronic carriers. They may subsequently develop chronic hepatitis, permanent liver damage or liver cancer.

Mode of transmission

Hepatitis B virus can be found in blood and body fluids of an infected person. It is spread in the following ways:
1. Mother to infant transmission at or around the time of delivery.
2. Blood contact
I. by direct contact with contaminated blood
II. by sharing contaminated personal items such as toothbrushes, razors and nail cutters
III. by sharing contaminated needles
IV. by ear-piercing, tattooing or acupuncture using contaminated instruments
V. by transfusion of contaminated blood or blood products
3. Sexual contact

Incubation period

The incubation period ranges from 45-160 days. Symptoms usually occur within 3 months.


For management of acute hepatitis, the patient should have adequate rest, balanced diet and avoid alcohol intake. Safer sex and practices to avoid transmission via blood contact should be encouraged.  Minority of adults who might become chronic carriers should receive individualized medical care for chronic hepatitis B infection.


1. Avoid sharing of syringes, razors, toothbrushes and other objects that may be contaminated with blood.
2. Clean and dress wound adequately.
3. Wear gloves while handling blood and body fluids.
4. Disinfect objects contaminated with blood using household bleach diluted 4 times. (1 part of bleach with 4 parts of water)
5. Practise safe sex.
6. An effective vaccine against hepatitis B infection is available. The standard vaccination scheme is a 3-dose schedule administered at 0, 1, 6 months. Booster dose is usually not required for those who have completed a standard three-dose regimen.
7. All babies born in Hong Kong are vaccinated. The birth dose is administered at birth in the hospital, while the second and third doses are given in Maternal & Child Health Centres. (Please refer to programme of immunization) For babies born to carrier mothers, an additional hepatitis B immunoglobulin is given within 24 hours of birth to prevent transmission of infection from their mothers.
8. After a 3-dose course of hepatitis B vaccination, babies born to mother infected with hepatitis B virus should receive post-vaccination serologic testing (PVST) to assess their immune response to vaccination and hepatitis B infection status. Please refer to the factsheet on PVST for more information.
9. Pregnant women with high HBV viral load may use antivirals in last trimester to reduce the viral load and the risk of mother-to-child transmission of HBV. Please refer to the website of Viral Hepatitis Control Office for more information.