Prevalence of HBsAg and HBsAg sub-types in the Canadian blood-donor population.

After 8 years of screening all blood donations in Canada for HBsAg, first by CIEP and later by RIA, the prevalence of HBsAg in the regular panel of "repeat" donors has been reduced from 267/10(5) to 39/10(5). Marked geographic variations exist, but the available data do not indicate whether the high prevalence of HBsAg in young adults, particularly males, may be a factor. The ad : ay subtype ratio across Canada is 2.0, but noticeable geographic differences are present, varying from 3.5 in Quebec to 0.5 in the Atlantic Provinces.