The prevalence of ay and ad subtypes of the hepatitis B surface antigen in Belgium.

Subtyping in various groups of persons positive for hepatitis B surface antigen gave the following results: Among asymptomatic blood donors (healthy carriers) subtype ad was found in 20, subtype ay in 24. Among symptomatic patients with acute hepatitis B ad was found in 25, ay in 29. Among patients of an institution for the mentally retarded ad was found in 9, ay in 23. Among patients of a Among patients of a geriatric institution ay was found in 9; among medical personnel of the same geriatric institution ay was found in 3 persons. Among symphilis patients ad was found in 6, ay in 29; and in patients of a dialysis centre ay was found in 6. These data show that neither subtype is really dominant in Belgium.