ORIGIN AND PREVALENCE OF HUMAN T-LYMPHOTROPIC VIRUS TYPE 1 (HTLV-1) AND TYPE 2 (HTLV-2) AMONG INDIGENOUS POPULATIONS IN THE AMERICAS

Human T-lymphotropic virus type 1 (HTLV-1) is found in indigenous peoplesof the Pacific Islands and the Americas, whereas type 2 (HTLV-2) is widelydistributed among the indigenous peoples of the Americas, where it appears to be moreprevalent than HTLV-1, and in some tribes of Central Africa. HTLV-2 is consideredancestral in the Americas and is transmitted to the general population and injectiondrug users from the indigenous population. In the Americas, HTLV-1 has more than oneorigin, being brought by immigrants in the Paleolithic period through the BeringStrait, through slave trade during the colonial period, and through Japaneseimmigration from the early 20^th century, whereas HTLV-2 was only broughtby immigrants through the Bering Strait. The endemicity of HTLV-2 among theindigenous people of Brazil makes the Brazilian Amazon the largest endemic area inthe world for its occurrence. A review of HTLV-1 in all Brazilian tribes supports theAfrican origin of HTLV-1 in Brazil. The risk of hyperendemicity in theseepidemiologically closed populations and transmission to other populations reinforcesthe importance of public health interventions for HTLV control, including therecognition of the infection among reportable diseases and events.