Natural history of hepatitis B virus infection in children.

Hepatitis B virus (HBV) infection during childhood can cause acute, fulminant or chronic hepatitis, liver cirrhosis, and liver cancer. Approximately 90% of the infants of hepatitis B e antigen (HBeAg) seropositive mothers become hepatitis B surface antigen (HBsAg) carriers. Children chronically infected are mostly asymptomatic. Although liver damage is usually mild during childhood, severe liver disease, including cirrhosis and hepatocellular carcinoma, may develop insidiously for 2-7 years. Spontaneous HBeAg seroconversion occurs gradually as the age of the child increases. Viral replication is reduced during this process, which is usually preceded by an elevation of aminotransferases. In a long-term follow-up study, the annual HBeAg seroconversion rate was 4-5% in children older than 3 years of age and less than 2% in children under 3 years. The annual seroconversion rate of HBsAg was very low (0.56%). Age at infection, maternal HBsAg and HBeAg status, host immune status, and possibly the HBV strain are the main factors determining the course of HBV infection in children.