Hepatitis B causes
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Hepatitis B |
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Hepatitis B causes On the Web |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor In Chief: Cafer Zorkun, M.D., Ph.D. [2]
Cause
For infants and children, the two primary sources of HBV infection are perinatal transmission from infected mothers and horizontal transmission from infected household contacts. Adolescents are at risk for HBV infection primarily through high-risk sexual activity (i.e., sex with more than one partner and male sexual activity with other males) and injection-drug use. Transmission of HBV via transfusion of blood and plasma-derived products is rare because of donor screening for HBsAg and viral inactivation procedures.
For a newborn infant whose mother is positive for both HBsAg and HBeAg, the risk for chronic HBV infection is 70%--90% by age 6 months in the absence of postexposure immunoprophylaxis. For infants of women who are HBsAg positive but HBeAg negative, the risk for chronic infection is <10% in the absence of postexposure immunoprophylaxis. Rare cases of fulminant hepatitis B among perinatally infected infants also have been reported. Studies suggest that breastfeeding by an HBsAg-positive mother does not increase the risk for acquisition of HBV infection in the infant.
Children who are not infected at birth remain at risk from long-term interpersonal contact with their infected mothers. In one study, 38% of infants who were born to HBsAg-positive mothers and who were not infected perinatally became infected by age 4 years. In addition, children living with any chronically infected persons are at risk for becoming infected through percutaneous or mucosal exposures to blood or infectious body fluids (e.g., sharing a toothbrush, contact with exudates from dermatologic lesions, contact with HBsAg-contaminated surfaces). HBV transmission rates to susceptible household contacts of chronically infected persons have varied (range: 14%--60%). High rates of infection also have been reported among unvaccinated long-term residents of institutions for the mentally handicapped, and, in rare instances, person-to-person transmission has been reported in child care settings.