Hepatitis B is a liver disease caused by the hepatitis B virus. Hepatitis B infection can lead to long-term liver disease. Left unmanaged, it can result in cirrhosis or liver cancer. More than two billion people worldwide have been infected by hepatitis B and of these over 240 million are living with long-term (also known as “chronic”) hepatitis B. Globally, there are over 780,000 deaths per year, from hepatitis B related causes - 650,000 from liver cirrhosis and liver cancer caused by hepatitis B, and 130,000 from acute hepatitis B.
In Australia, there are over 380 deaths each year from hepatitis B and recent research shows that more than 213,300 people are living with chronic hepatitis B. The majority of people in Australia with chronic hepatitis B come from one of the following:
- People from countries of high hepatitis B prevalence, especially North-East Asia, South-East Asia and sub-Saharan Africa.
- Aboriginal and Torres Strait Islander people
- People who inject drugs
- Men who have sex with men
Hepatitis B disease progression
If you have hepatitis B for less than six months and recover from it, it is called an acute infection. In rare cases, fulminant hepatitis (acute liver failure) may develop during the acute infection phase and this may be fatal. If the infection lasts longer than six months, it is known as chronic hepatitis B.
Nine out of ten adults infected by hepatitis B will naturally clear the virus and develop immunity for life. In contrast, 9 out of 10 children who are infected will not clear the virus and will go on to develop chronic hepatitis B. Left untreated, 20 to 30 per cent of people with chronic hepatitis B will develop serious liver disease including liver cancer.
There are four phases of disease development for chronic hepatitis B:
- Immune tolerance phase
This phase often lasts from birth or early childhood to early adulthood. In this phase, the level of hepatitis B virus in the blood is high but liver damage is not occurring. When the virus infects the body in childhood, the immune system does not recognize it as a threat. Because the immune system doesn’t recognise the threat, it takes no action against the virus so there is little or no damage to the liver despite the high viral load.
- Immune clearance phase
This is when the immune system tries to clear the virus. Due to the activity of the immune system on the virus in the liver cells, this phase is when most damage is done to the liver. It is important for doctors to know when the disease moves into this phase as treatment at this stage will reduce the risk of severe liver disease. If no treatment is given at this stage, there may be permanent liver damage.
- Immune control phase
In this phase, the level of hepatitis B virus is low and there is no obvious liver damage. In the past, people at this stage were referred to as “healthy carriers”. However, recent studies have shown that the hepatitis B virus can reactivate and there is no such thing as a “healthy carrier”. It is important to maintain monitoring in case the virus reactivates.
- Immune escape phase
In some people, the hepatitis B virus changes and the immune system is unable to control it. This phase usually occurs in adulthood and can lead to further liver damage. It is important for doctors to identify when this stage occurs so that treatment can be considered to reduce the risk of severe liver disease including liver cirrhosis and liver cancer. Liver cancer can occur even when liver damage is not severe.
Hepatitis B symptoms
Initially after infection, some adults may experience fatigue, fever, nausea, vomiting, loss of appetite, bloating, indigestion, headaches, itching, joint or muscle pain and jaundice – a yellowing of the skin and eyes. However, many people don’t notice any symptoms at all and don’t know they have recently been infected. Children usually don’t experience any symptoms.