Relatively little is known about the risk of transmission of hepatitis B virus (HBV) in day-care centers; the virus is primarily spread by blood and other body secretions. Gradual horizontal transmission of hepatitis B has been observed in homes for the mentally retarded.1-3 Horizontal spread in children appears to be of equal importance with vertical transmission in countries where hepatitis B is endemic.4 These infections, which usually are asymptomatic, may result in chronic carriage and may go undetected unless children are tested for hepatitis B markers. Studies in day-care centers in Okinawa, where HBV carriage is relatively common, suggest that transmission may occur in day-care centers.5 Case reports of HBV transmission in school or day-care settings in the US6 and Italy7 have been published.Our study was undertaken to determine whether there is evidence of horizontal transmission of HBV infections in US day-care facilities. To evaluate this, we screened for the antibody to hepatitis B core antigen (anti-HBc), a marker which is seen both in those who have recovered from hepatitis B and those who are carriers.8 Capillary blood specimens, obtained by finger prick, were used. Children who tested positive had venous blood specimens drawn and their families were approached for consent to draw venous specimens also from the household members to evaluate if the infection may have originated in the family. The venous specimens were tested also for additional markers, especially for hepatitis B surface antigen (HBsAg), which is found during acute infection and in carriers, and antibody to HBsAg (anti-HBs) which develops after infection and immunization.
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