The epidemiological importance of 'ay' and 'ad' subtypes of the HB-Ag.

The distribution of the subtypes ;ay' and ;ad' has been assessed in 159 hepatitis B antigen (HB-Ag) positive subjects with a variety of associated hepatic conditions. A specific subtype could not be correlated with any particular hepatic pathology when the whole group was considered. However, the distribution of these two subtypes did vary according to the geographical origin of the subject or infection, or the presumed route of infection, so that there was an apparent association of one subtype with a certain disease state. Subtyping performed on 10 HB-Ag-positive households showed the subtype to be the same within nine, emphasizing the epidemiological rather than the pathological importance of the ;ay' and ;ad' subtypes of the HB-Ag.