Hepatitis B antigen in Montréal blood donors: childhood institutionalization as an epidemiologic factor.

In 1971 the Canadian Red Cross blood tranfusion service instituted routine screening for HBAg of all blood donors, using nationwide a standardized counterimmunoelectrophoretic technique. The prevalence of carriers in the Province of Québec is unusually high (0.51%), being 3 to 12 times higher than in the other nine provinces. Among the carriers found in the Montréal area 289 volunteered to be seen by our group for an extensive interview and a series of laboratory tests. There were 243 men and 46 women; their ages ranged from 18 to 55, 90% being less than 40. Twenty-nine were of foreign origin and 260 were born in Canada. The epidemiologic data revealed that the reservoir of HBAg carriers among the blood donors of the Montréal area was found predominantly in the autochthonous population of French origin. Moreover, it appeared that 149 (52%) had lived in institution when they were infants or children: 127 were orphans and had been placed in institutions as newborns or babies, and 22 others had lived in institutions for at least 1 year between the ages of 5 and 10. This was by far the most important single epidemiologic factor that could contribute to the explanation of the abnormally high prevalence of HBAg carriers in the population studied.