Hepatitis B

Causative agent

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

Clinical features

The virus can cause acute hepatitis. Infants and young children are mostly asymptomatic when newly infected with HBV, while 30–50% of older children or adults with acute hepatitis B may develop symptoms that are undistinguishable from hepatitis of other causes. Common presentations include fever, fatigue, loss of appetite, nausea, vomiting, upper abdominal pain, jaundice (yellowing of the skin and the whites of the eyes), dark (tea-coloured) urine and pale stools.

Symptomatic or not, some people fail to clear the virus and develop chronic hepatitis B (CHB). The younger a person is when infected with HBV, the higher the risk of developing chronic infection. Up to 90% of newborn babies infected with HBV would develop CHB, while the risk for adults is about 5%. Chronic HBV infection could lead to 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-child 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 30 to 180 days, with an average of 75 days.

Management

There is no specific treatment for acute hepatitis B. 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.

For chronic hepatitis B, antiviral medication is effective in inhibiting HBV replication and reducing the risk of cirrhosis, liver failure and liver cancer. People with CHB should have regular medical follow-up and relevant investigations, to determine when antiviral medication is needed and detect changes in the liver condition early for management.

Prevention

1. Avoid sharing of syringes, razors, toothbrushes and other objects that may be contaminated with blood.
2. Clean and dress wound properly.
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 safer sex and use condom properly.
6. Receive hepatitis B vaccination. 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 after 1988 are vaccinated. The birth dose is administered at birth in the hospital, while the second and third doses are provided in Maternal & Child Health Centres (Please refer to programme of immunisation). For babies born to mothers with hepatitis B, an additional hepatitis B immunoglobulin is given within 24 hours of birth to prevent transmission from their mothers.
8. After a 3-dose course of hepatitis B vaccination, babies born to mother with hepatitis B 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.