Hepatitis B is a disease caused by a DNA virus. The transmission is by blood (wounds, sexual relations, transfusions, accidents with contaminated material, etc.). The most common form of the disease is chronic, the infected patient carries the virus for life and the liver gradually suffers injuries that can lead to cirrhosis or even to hepatic cancer.
Another form of the disease is acute, sometimes fulminating, with symptoms similar to those of hepatitis A but more severe and sometimes lethal. There are persons that are asymptomatic carriers of the virus. The level of hepatic injury is assessed by blood tests of hepatic enzymes and by hepatic biopsy (extraction of small samples of tissue to be examined under the microscope). Viral replication can be estimated through PCR (polymerase chain reaction).