Once the hepatitis B virus has infected a liver cell, it makes lots of copies of itself. They travel around your body in your blood. When this is happening, if your blood mixes with someone else’s, the virus can get passed on.
The virus also makes proteins called antigens – there are 2 main types envelope (e) antigen and surface (s) antigen. They are part of the outside of the virus and also get onto the outside of infected liver cells.
Your immune system recognises the antigens as things that aren’t meant to be there and attacks them. This reduces levels of the virus. Over time the virus stops making the e- antigen. This is usually a sign that it is coming under control.
Inflammation, fibrosis and cirrhosis
Your immune system also attacks and kills the infected liver cells. This causes inflammation and damage in your liver. Your liver is good at repairing itself. But if it gets damaged again and again your liver can get scars (called fibrosis).
If your liver gets lots of scars, this is a stage of liver disease called cirrhosis. Your liver can stop working properly and you can become very ill. The damage to your liver also increases the chances of developing liver cancer.
Acute hepatitis B
If your immune system works well, it can kill the virus and all the infected liver cells quickly. Your liver can repair the damage and most people have no lasting problems. This is what happens in acute hepatitis B.
Chronic hepatitis B
In chronic hepatitis B, your immune system and the virus are in a standoff. Your immune system keeps trying to get rid of the virus by killing infected liver cells. But the hepatitis B virus can stop your immune system working properly or hide from it.
Chronic hepatitis B has different phases or stages, depending on what the virus and your immune system are doing.
The main tests your doctor uses to check on the phase of the infection are:
- Levels of virus DNA in your blood – the higher these are, the more virus there is.
- Levels of hepatitis B envelope antigen (HBeAg) – high levels mean the virus is copying itself.
- Levels of alanine aminotransferase (ALT) – high levels mean your liver is being damaged.
There are 5 phases, but they do not always happen in order and you might not have some of them. There are also grey areas where the infection shows a mix of phases.
|Phase 1||Phase 2||Phase 3||Phase 4||Phase 5|
|What’s happening?||The virus is making lots of copies of itself but isn’t damaging the liver.||The immune system is attacking the virus. The liver is being damaged.||The virus is under control, but it hasn’t gone away. It is not damaging the liver. And the immune system isn’t being triggered.||The virus is making some copies of itself. The immune system is responding and the liver is being damaged.||The virus is still there but is not active. It no longer makes envelope or surface antigen. The liver isn’t being damaged.|
|Chance the virus can be passed on||High||High||Very low to none||Low||Very low to none|
|DNA levels in the..||Millions||Hundreds of thousands||Thousands or lower (can be undetectable)||Thousands to tens of thousands||Usually undetectable|
|Envelope antigen being made?||Yes||Yes||No||No||No|
Phase 3 used to be called being a ‘carrier’ and you might still hear that term. The name was changed because it was hurtful to people living with hepatitis B. So the British Liver Trust and many doctors and nurses no longer use it.
Published July 2023
Review due: July 2026