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Hepatitis B - Background information
What is it?

  • Hepatitis B is an infectious disease of the liver caused by the hepatitis B virus.
    • Hepatitis B is an enveloped DNA virus of the family hepadnavirus. It consists of a core antigen surrounded by a surface antigen.
    • The hepatitis B virus has eight distinct genotypes (A to H) which vary in geographical distribution. The different genotypes cause diseases that differ in severity and which respond differently to treatment.
  • Acute hepatitis B is a notifiable disease.
    • In adults and older children, it is usually a self-limiting condition marked by inflammation in the liver and transient infection.
    • In infants and younger children, it is generally asymptomatic, but usually results in chronic infection.
  • Chronic hepatitis B is not a notifiable disease. It occurs when there is failure of the immune system to clear the virus; causing the infection to persist.
    • Chronic infection occurs for reasons that are not fully understood, but are in part determined by genetic factors and the maturity of the host immune response.
    • Hepatitis B virus-infected hepatocytes become inflamed and necrotic; not as a direct result of infection, but through a cytolytic T-cell response of the host. The resultant liver damage may eventually lead to cirrhosis and hepatocellular cancer.

[BASHH, 2008; Dienstag, 2009; James-Koziel and Thio, 2009; HPA, 2010a]

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