What is Hepatitis?
Hepatitis is inflammation of the liver. It has a number of different causes, but the most common is damage by a virus. Hepatitis B is one of the viruses which can damage the liver. Others include the Hepatitis A, C, D and E viruses, and sometimes the Epstein-Barr (EBV or Glandular Fever) virus and cytomegalovirus (CMV).
How does Hepatitis B virus damage the liver?
The Hepatitis B virus (HBV) multiplies in the liver cells. The body then tries to get rid of the Hepatitis B by killing the infected cells. Ironically, it is the self-defence, or immune response which does the most damage to the liver.
How is Hepatitis B spread?
Hepatitis B is spread by contact with blood and other bodily fluids, usually through a breach in the skin or contact with internal lining surfaces of the body. The various ways people can acquire Hepatitis B include :
- From a carrier mother to her baby at around the time of birth. This is the most common way for the virus to spread in some parts of the world.
- By use of injecting drugs (at any time in the past or present)
- By sexual contact
- By blood transfusion. This is fortunately extremely rare these says, as blood in Australia is tested for Hepatitis B before it is transfused.
- By tattooing with unsterilised needles
- By close family contact
- By accidental inoculation (needle stick injury) or splashing with infected blood or secretions (eg. some groups of health care workers)
What damage can Hepatitis B do?
The outcome of Hepatitis B infection depends largely on the age at which it is contracted. Babies who are infected with the Hepatitis B virus at birth, almost always go on to become long-term (‘chronic’) carriers of the virus. However the infection at birth is silent, and the babies appear healthy and do not become jaundiced (turn yellow). Such people generally appear perfectly healthy for many years, but after 20, 30, 40, or 50 years they can become unwell. Chronic carriers who acquire their infection early in life have an overall chance of approximately 25% of developing cirrhosis (scarring of the liver) or even liver cancer during their lifetime.
If a teenager or adult becomes infected with the hepatitis B virus there is about a 50% chance that they will become ill and develop jaundice (or turn yellow). This illness is called acute hepatitis. However, in the other 50% of cases, there is no jaundice and the infection is silent (or ‘subclinical’). Adults have a good chance (between 90-95%) of being able to get rid of the virus, or ‘clear’ the virus from the body. Individuals who have been infected and clear the virus are immune to the disease and do not develop long-term liver damage.
In approximately 5-10% of cases, adults are unable to clear the virus, and become long-term, ‘chronic’ carriers. Generally such people remain in good health for many years. However there is an increased chance that chronic carriers of the Hepatitis B virus will develop cirrhosis or liver cancer over many years or decades.
How can we tell if you are infected with HBV and whether you have any liver damage?
There are many tests that can assist doctors in assessing liver damage, or likelihood of future liver damage from Hepatitis B. The interpretation of these tests is not always straightforward, and sometimes specialist advice is needed. Some of the more important tests are :
- Hepatitis B surface antigen : This is the test to see whether or not you are infected with the Hepatitis B virus.
- Hepatitis B e antigen : This blood test tells the doctor whether or not the virus is continuing to multiply in the liver. People who have HBe antigen are more infectious to others than those who don’t. They are also generally at greater risk of continued liver damage.
- Hepatitis B virus DNA : This is another test for activity or replication rate of the virus.
- Hepatitis B surface antibody : this blood test is positive if someone has had Hepatitis B, cleared the virus, and is now immune. People who have had successful Hepatitis B vaccination also usually have a positive Hepatitis B surface antibody, indicating that they are immune.
- Liver function tests : Blood tests which give an estimate of liver inflammation or damage. The ‘ALT” or (alanine amino transferase) test is a reasonably good guide. Other parts of the liver function tests can help the doctor assess whether or not there are may be cirrhosis.
- Liver ultrasound or scan : These tests use inaudible sound waves (sonar) to give the doctor pictures of the liver and can assist in diagnosing cirrhosis or liver cancer.
- Liver biopsy : This is the removal of a tiny piece of liver under local anaesthetic, and is used on occasions to assess damage n the liver.
- Alpha-fetoprotein : Is a blood test which can sometimes detect liver cancer.