Geographical distribution of HBs Ag in Africa.

The incidence of HBs Ag carrier is high in Africa. The HBs Ag subtypes vary in 5 mean areas of the Africa continent. The subtype ayw4(a3) is the most characteristic African subtype, being found with a striking frequency in West Africa (88.8%). In North Africa ayw2(a21) is predominant as in other mediterranean countries. In Saharan area mixed types of HBs Ag are found, intermediary between North and West Africa. In Central Africa y is predominantly associated with w2(a21) or with w4(a3). In east and South Africa ad is largely predominant and the most widespread subtype is adw2(a21). No adr, nor adw4 were found in Africa.