Hepatitis B is a liver infection caused by the hepatitis B virus (HBV). HBV is one of five types of viral hepatitis. The others are hepatitis A, C, D, and E. Each is a different type of virus. Types B and C are most likely to become chronic, or long lasting.
Acute hepatitis B causes symptoms to appear quickly in adults. Infants who contract it at birth rarely develop only acute hepatitis B. Nearly all hepatitis B infections in infants go on to become chronic.