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Hepatitis B

  • Hepatitis B is a liver disease caused by hepatitis B virus (HBV) infection.
  • The incubation period ranges from 30 to 180 days, with an average of 75 days.
  • 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, such as fever, fatigue, loss of appetite, nausea, vomiting, upper abdominal discomfort, tea-coloured urine and jaundice (yellowing of the skin and the whites of eyes).
  • 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%.
  • CHB is a lifelong infection and may lead to acute liver failure. About 15-40% of persons with CHB could develop cirrhosis and liver cancer.
  • HBV infection may remain asymptomatic until signs and symptoms develop secondary to serious liver damage.
    HBV infection

Epidemiology in Hong Kong

  • According to an epidemiological study conducted in 2015-16, about 7.2% of the Hong Kong population had been infected with HBV.
  • In 2020, about 3.4% of pregnant women had been infected with HBV in Hong Kong.

Transmission of hepatitis B

  • HBV can be transmitted from mothers with CHB to their babies during delivery. In endemic places, most persons with CHB acquired HBV infection by mother-to-child transmission (MTCT). Please click here more information about MTCT of hepatitis B.
  • HBV can also be transmitted through contact with blood or body fluids of an infected person:
    • contact with an infected person's blood or body fluids through broken skin, or mucosal membranes of the eyes or mouths
    • sharing injection instruments for drug injection
    • using contaminated instruments for ear-piercing, tattooing or acupuncture
    • sharing personal items, which may be contaminated with blood, such as razors, shavers and nail trimmers
    • reusing inadequately sterilised medical equipment
    • transfusion of contaminated blood or blood products
  • Unprotected sexual contact with an infected person can also spread HBV.
  • HBV is not transmitted through breastfeeding or social contact, such as sharing eating utensils, dining together, hugging, shaking hands and kissing.


Persons considered at higher risk of HBV infection should get tested

HBV infection should get tested
  • Family members (such as parents, siblings and offspring) and sexual partners of people with CHB
  • People who inject drugs
  • Men who have sex with men
  • HIV-positive people
  • People who receive blood or blood products on a regular basis
  • People on dialysis
  • Healthcare workers who may have occupational exposure to blood or body fluids of patients


Blood test is required to diagnose hepatitis B

  • The test generally consists of blood tests on hepatitis B surface antigen (HBsAg) and hepatitis B surface antibody (anti-HBs)

Hepatitis B surface antigen (HBsAg)

  • People with a positive HBsAg result are currently infected with HBV and should seek medical consultation as soon as possible.
  • If HBsAg result is positive for more than 6 months after HBV infection, this means CHB has developed.

Hepatitis B surface antibody (anti-HBs)

  • A positive anti-HBs result means that the person has adequate hepatitis B antibodies for protection against HBV infection.
  • Protective antibodies can be acquired after hepatitis B vaccination or recovery from past HBV infection.
Test results Clinical interpretation
HBsAg Anti-HBs
Positive ( + ) Negative ( – )
  • Infected with HBV
  • Should seek medical consultation as soon as possible
Negative ( – ) Positive ( + )
  • No HBV infection
  • Have adequate protective antibodies against HBV infection
Negative ( – ) Negative ( – )
  • For blood testing on hepatitis B, you may consult your family doctor. You may wish to refer to the Primary Care Directory to find a suitable family doctor. Please contact the doctor directly for details of service, charges and respective arrangement.


Treatment of hepatitis B

  • Antiviral medication is effective in inhibiting HBV replication and reducing the risk of cirrhosis, liver failure and liver cancer.
  • Doctors will thoroughly assess the condition of each patient with CHB to determine when antiviral medication is needed.
  • Patients with CHB should have regular medical follow-up and relevant investigations, such as blood test for liver function, alpha-fetoprotein and viral load, and ultrasonographic abdominal examination, for early detection and management of changes in the liver condition.
  • Patient with CHB must take the antiviral medication as prescribed. Do not self-discontinue the medication even when the viral load is suppressed or the liver function is restored to normal. Inappropriate interruption of antiviral treatment may lead to hepatitis B reactivation, liver failure and even death.

Points to note for people with CHB

  • Have regular examination for early detection of changes in the liver condition, such as blood test for liver function, alpha-fetoprotein and viral load, and ultrasonographic abdominal examination
  • Follow doctor’s instruction to receive treatment and follow-up
  • Maintain healthy diet and lifestyle
    • Do not smoke or drink
    • Maintain balanced diet with abundant fresh vegetables and fruits
    • Avoid eating raw or undercooked shellfish
    • Do not take medication with uncertain ingredients to avoid liver damage
    • Be physically active and maintain healthy body weight
  • Adopt preventive measures to stop HBV transmission
    • Wear gloves while handling open wounds with care and bandage them properly
    • Do not share personal care items which may be contaminated with blood, such as razors and nail scissors
    • Do not share needles or any other injecting equipment
    • Practice safer sex and use condom properly during sexual intercourse
    • Disinfect items contaminated by blood or body fluids with household bleach and gloves on
    • Family members and sexual partners should take a blood test as soon as possible, and receive vaccination if found to be non-immune and not infected with HBV

Hepatitis B vaccination

Hepatitis B vaccination is effective to prevent HBV infection. Please click here for more information about hepatitis B vaccination.


Health education materials

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