Distribution of HBsAg subtypes in the world.

HBsAg subtyping was performed in 5,337 sera from chronic carriers who originated from 54 different countries of the 5 continents. Nine subtypes were defined: ayw1, ayw2, ayw3, ayw4, ayr, adw2, adw4, adr q- and adr q+. The repartition of these subtypes, according to the country of origin of the carriers, enhances the previous results and supplies new data: ayw1 is prevalent only in Vietnam (51%); ayw2 in Mediterranean countries (73%); ayw3 in Greece and Yugoslavia (54%) along with ayw2 (41%); ayw4 in West Africa (82%) and Central Africa (42%) along with ayw2; ayr was only found in Vietnam (3.4%); adw2 is prevalent in North and Central Europe (70%), East and South Africa (95%), India (55%), along with ayw3 (35%) in northern South American (74%), and in the Antilles (82%); adw4 is widespread in French Polynesia (45%)--with a 100% frequency in the Marquesas archipelago--as well as in Argentina (42%); adr q--was found only in Ocean: French Polynesia (34%) with a 69% frequency in the Australes, New Caledonia (3 out of 3 HBsAg carriers); adr q+ is the prevalent subtype in South-East Asia if we exclude Vietnam (61%). These results show that a precise geographical distribution of HBsAg subtypes needs more than 'four main subtypes' generally used. Enlarging from 4 subtypes to 9 is a requirement for valuable epidemiologic studies, as well as for the specification of anti-HBs antibodies produced by hybrids or induced by synthetic peptide. The geographical distribution of these 9 HBsAg subtypes and the serological relationship between some determinants suggest a genetic recombination of viral DNA.