hepatitis B (HB), a viral hepatitis caused by the hepatitis B virus (HBV), a hepadnavirus. The virus is transmitted by transfusion of contaminated blood or blood products, by sexual contact with an infected person, by the use of contaminated needles and instruments, or in utero. It can cause acute and chronic hepatitis. Ninety-five percent of patients clear the infection and develop antibodies to HBV. The remaining 5% who are unable to clear the virus develop chronic infections that put them at risk for long-term complications. Severe infection may cause prolonged illness, destruction of liver cells, cirrhosis, increased risk of liver cancer, or death. A vaccine is available and recommended for infants, teenagers, and adults at risk for exposure. Treatment may involve transplantation. Also called serum hepatitis. See also viral hepatitis.
