[Natural history of viral hepatitis].

Acute hepatitis B is associated with a risk of evolution to chronic hepatitis in 90% of cases in the newborn, 50% in the childhood and 5 to 10% in adults. During the chronic phase, we usually distinguish 4 phases: the immunotolerance phase with a positive HBe antigen, ALT in the normal value, high viral load and the absence of necro-inflammation; then the phase of immune clearance associated with fluctuations of the viral load and ALT level, HBe antigen seroconversion and histological lesions of chronic hepatitis; at this phase, we distinguish the HBe antigen positive chronic hepatitis B and the HBe antigen negative chronic hepatitis B, called "mutant virus" which is the main chronic hepatitis 8 observed in France. The treatment is usually discussed during this chronic hepatitis phase. The third phase is called inactive chronic carriage and is associated with no detectable viral replication, normal ALT and the absence of necro-inflammation. A fourth phase is possible with viral reactivation episods. Hepatitis C leads to chronic hepatitis in 2/3 to 3/4 of cases. Factors associated to the progression of the disease are the age of patient at the time of contamination, the male gender, alcohol consumption, HIV co-infection and metabolic factors, especially steatosis. These factors increase the risk of progression of the disease and the evolution to cirrhosis and hepatocellular carcinoma.