Chapter 4: Hepatitis B I. Disease Description

Winston Abara, Sarah Schillie
Hepatitis B is caused by infection with the hepatitis B virus (HBV), a double-stranded DNA virus of the family hepadnaviridae. HBV replicates in the liver and causes both acute and chronic hepatitis. Although the highest concentrations of virus are found in blood, other body fluids, such as semen and saliva, have also been demonstrated to contain HBV. HBV is predominantly a blood and sexually transmitted infection and is transmitted by percutaneous and mucosal exposure to infectious body
more » ... ectious body fluids. Symptomatology and transmission The incubation period for acute hepatitis B ranges from 45 to 180 days (average 120 days). The clinical manifestations of acute HBV infection are age dependent. Infants, young children (younger than 10 years of age), and immunosuppressed adults with newly acquired HBV infection are usually asymptomatic. 1 Older children and adults are symptomatic in 30%-50% of infections. When present, clinical symptoms and signs might include anorexia, malaise, nausea, vomiting, abdominal pain, jaundice, dark urine, and clay-colored or light stools. Occasionally, extrahepatic manifestations occur and include skin rashes, arthralgia, and arthritis. Fulminant hepatitis occurs in about 1%-2% of acutely infected persons. Among adults with normal immune status, most (94%-98%) recover completely from newly acquired HBV infections, eliminating the virus from the blood and producing neutralizing antibodies that confer immunity from future infection. 2 In infants, young children, and immunosuppressed persons, most newly acquired HBV infections result in chronic infection. 3, 4 Infants are at greatest risk, with a 90% chance of developing chronic infection if infected at birth. 5 Although the consequences of acute hepatitis B can be severe, most of the serious sequelae occur in persons in whom chronic infection develops. Chronic liver disease develops in two-thirds of these persons, and approximately 15%-25% die prematurely from cirrhosis or liver cancer. Persons with chronic HBV infection are often detected in screening programs, such as those for blood donors, pregnant women, and refugees. 6, 7 Persons with chronic HBV infection are a major reservoir for transmission of HBV infections. Any person testing positive for hepatitis B surface antigen (HBsAg) is potentially infectious to both household and sexual contacts.