Definition of hepatitis B
: an acute or chronic hepatitis that is caused by a DNA virus (species Hepatitis B virus of the genus Orthohepadnavirus, family Hepadnaviridae), is marked chiefly by fatigue, fever, nausea, vomiting, abdominal pain, darkened urine, jaundice, and joint pain but may be asymptomatic, and is transmitted especially by contact with infected blood (as by transfusion or by sharing contaminated needles in illicit intravenous drug use) or by contact with other infected bodily fluids (such as semen)
Note:
The acute form of hepatitis B, a mild illness lasting several weeks to months, may progress to long-term or chronic infection often leading to liver damage, liver failure, or liver cancer.
— called also
serum hepatitis 
