Hepatitis B is an infection of the liver caused by the hepatitis B virus (HBV). The same virus produces two very different diseases: an acute, self-limited hepatitis that most adults clear, and a chronic infection, defined by the virus persisting in the blood for more than 6 months, that can last for life and progress to cirrhosis (scarring of the liver) and liver cancer. Which course an infection takes depends mainly on the age at infection and on the strength of the immune response.
That single idea organises the topic: who is exposed and when, what the virus is and how it multiplies, how the immune response injures the liver or fails to, and how the resulting disease is recognised, classified and treated.
Where to start
A reader new to hepatitis B can begin with how the infection spreads and then follow it through the virus, the injury it causes, the clinical picture, the blood tests that define the phase, the complications and the treatment. Each note below answers one of those questions.
- Hepatitis B Transmission and Epidemiology — how HBV spreads, which groups carry the highest burden, and how its frequency varies between regions.
- Hepatitis B Virus Structure and Antigens — the Dane particle, its surface and core antigens, and the subviral particles released into blood.
- Hepatitis B Virus Replication — how HBV copies its genome through an RNA intermediate and releases non-infective decoy particles.
- Pathogenesis of Hepatitis B — why the immune response, rather than the virus alone, causes most of the liver injury, and how immune tolerance shapes infection in the newborn.
- Clinical Presentation of Hepatitis B — what acute and chronic hepatitis B look like, from silent infection to fulminant hepatitis.
- Hepatitis B Serologic and Virologic Markers — the sequence of HBsAg, anti-HBs and anti-HBc that separates acute from chronic infection, and the window between them.
- Complications of Hepatitis B — serum sickness-like illness, chronic hepatitis, cirrhosis and hepatocellular carcinoma.
- Treatment of Hepatitis B — how acute disease is supported and how chronic infection is suppressed with antivirals.