Discussion:
Hepatitis B is transmitted by blood and other body fluids. Routes of infection are:

• percutaneous - injection drug use, exposure to contaminated blood or body fluid
• sexual - heterosexual or male homosexual activities
• vertical - i.e. from mother to infant
• horizontal - i.e. between children and household contacts through skin lesions or sharing of blood-contaminated toothbrushes and razors.

Thus major risk factors for acquiring hepatitis B are injection drug use and high risk sexual activity (multiple partners, HBV+ partner). Other risk factors include:

• hepatitis B carrier in the family
• male homosexual activity
• institutionalization
• blood transfusion
• occupational blood contact ( hospital workers and dentists)
• body piercing
• history of hospitalization/surgery/dental visit.

Exposure to HBV has no effect in an immune person or if the infecting dose is inadequate, but the non-immune person may develop acute hepatitis which may range from asymptomatic/subclinical to fulminant. The infection may be cleared or the person may become a carrier. A carrier may remain 'healthy' with near normal liver histology or develop chronic hepatitis. Some with chronic hepatitis will progress to cirrhosis. Any carrier, 'healthy' or not, may develop hepatocellular carcinoma.

Ninety to 95% of infected neonates become carriers. In most the disease is mild and only occasionally progressive. In adults acute hepatitis B is more severe, but only a minority become carriers (1-10%). Fifteen to 40% of carriers develop develop serious sequelae and eventually chronic hepatitis ± cirrhosis.

Hepatitis B infection can be prevented by immunization, passive or active.

Other causes for chronic hepatitis are hepatitis C, hepatitis D (with hepatitis B), some drugs, autoimmune hepatitis, Wilson's disease, and alpha-1 antitrypsin deficiency. In some cases of chronic hepatitis, the etiology is unknown (idiopathic).