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Hepatitis B

The Hepatitis B virus

This is a virus that multiplies in the liver and can cause liver damage.


  • One third of the world’s population have past or present infection with the Hepatitis B virus.
    • There are 350 million with chronic Hepatitis B infection in the world.
    • There are probably over 90,000 people in New Zealand with chronic infection.
    • Only 30,000 have been identified - the rest do not know they have the infection. The National screening program attempted to find these people with chronic infection and was only partially successful.
    • The rate of carriage of Hepatitis B is 6-8% for Maori, Pacific Islander and Asian populations but less than 1% for Europeans. There are very high rates of chronic infection in some Pacific Island groups (e.g 13% in Tongans).
  • Hepatitis B virus is spread through blood and other body fluids (including saliva). The infection can be caught by:
    • Most commonly the infection is acquired at childbirth (mother to child) OR from close contact of children in early childhood.
    • Less common and relevant to adult infection are sexual contact, sharing of needles, tattooing equipment, sharing personal items (razors, toothbrushes), needle-stick injuries (health care workers).



Outcomes of the infection

  • There are a wide range of outcomes of the infection depending to a large extent on the age at which the infection is acquired.
    • Overall most people who are exposed to Hepatitis B will become immune.
    • This means the virus has been cleared. There are no problems with health in the longer term.
    • Infection acquired as an adult is more likely to lead to a “hepatitis” illness with jaundice. The majority of people with adult infection become immune.
    • Infection as a newborn (at delivery) or in the first 5 years of life has a high chance of developing chronic (long-term) infection.Most infections are “silent” - not picked up at the time because there were few symptoms. Men have a higher chance of developing chronic infection.
  • If chronic (persistent/ ongoing) infection develops there are two main outcomes.
    • Inactive infection. This can be called a “carrier” state. The virus is relatively dormant. Liver tests stay normal throughout life.There are minimal risks of liver disease over a lifetime.
    • Active infection. There is "active" turnover and multiplication of the virus. There is inflammation in the liver and the potential for liver damage. The body’s immune system is trying to kill the virus (without success). In the process the immune system is causing liver cells to die.
    • This usually means having the Hepatitis B 'e' antigen. Some people over time develop a mutant form of the virus that does not express the 'e' antigen.
    • For a young adult (less than 30 years) with active disease there is a reasonable chance that the immune system with be able to get on top of the infection. This is called seroconversion because a protective antibody is formed. Unfortunately it is more common that the infection continues to be active and there is slow but progressive damage to the liver.
  • The long-term risk is the development of cirrhosis (scarring of the liver) and the risk of developing liver cancer.
    • The risk is 20% over 20 years for active infection.  In NZ there are about 10 liver transplants performed per year for hepatitis B.  In NZ there are over 200 liver related deaths per year from hepatitis B.




Diagnosis

  • The presence of the virus in the liver is determined by the Hepatitis B surface antigen test.
  • Active "turnover" (replication) of the virus is detected by;
    • Having the Hepatitis B e antigen.
    • Or by having high levels of virus DNA in the blood.
  • The degree of the inflammation in the liver.
    • Can be determined to some extent by the liver blood tests (liver enzymes ALT and AST) but a liver biopsy is the most accurate assessment.




Goals of therapy in chronic hepatitis B

  • The main goals of treatment:
    • Completely getting rid of the virus from the body is rarely possible therefore converting the infection to an "inactive" state is the main goal.
    • This is measured by loss of e antigen or the  absence of Hepatitis B DNA in the blood.
    • Liver enzyme tests should return to normal - this suggests that liver inflammation had subsided.
    • Improvement in symptoms is actually not a main goal as the infection often causes no symptoms until there is advanced liver disease.
    • Prevention of progression of liver disease and prevention of liver cancer.  This is hard to prove for any particular treatment but it seems that any treatment that leads to normal liver tests for a significant period of time reduces the risk of serious complications.


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