Formerly called serum hepatitis, it is caused by the hepatitis B virus (HBV). About 10 percent of cases progress to chronic hepatitis. It is spread through intravenous drug use, through sexual contact with infected individuals, through exposure to infected body fluids, and vertically from mother to child. Common symptoms include abdominal pain, fatigue, fever, jaundice, and elevated liver enzymes. A vaccine against HBV is available.