Human T-lymphotropic virus 1 (HTLV-1) was discovered in 1980 as the first human retrovirus. As zoonosis, HTLV-1 derives from jumps to humans from simian T-lymphotropic virus naturally infecting monkeys in Central and Western Sub-Saharan Africa for thousands of years. Molecular clock study estimates an ancestor for all human HTLV-1s around 30,000-40,000 years ago. As expected, Africa accounts for the largest number of HTLV-1 infections worldwide. However, Latin America is the second region endemic for HTLV-1 globally. As shown in figure 1, four areas of high HTLV-1 prevalence can be recognized, namely, at the Caribbean basin, Brazil, Peru, and along the Andes mountains. Phylogenetic studies have examined viral sequences from isolates in all these regions, including the exam of older mummies. Based on these data, a reconstruction of the earliest introduction and dissemination of HTLV-1 in America can be postulated.