[HTLV-1 infection in time and space]

Human T-cell leukemia virus type 1 (HTLV-1) is a member of the Oncoretrovirinae family containing several viruses that have been associated with a low incidence of leukemia and sarcoma in mammals. Primates are susceptible to viruses of genera HTLV (humans) and STLV (other primates). The high degree of homology in genomic arrangement of HTLV and STLV is probably due to the existence of a common simian ancestor. Most infections are asymptomatic but a few cases exhibit blood diseases, e.g., T-lymphoma or T-cell leukemia, or neurologic disease, mainly, HTLV-1 associated myelopathy and tropical spastic paraparesia (HAM-TSP). The four major modes of viral transmission are vertical transmission from mother to child either in utero or, more commonly, during breastfeeding, sexual intercourse, blood transfusion, and intravenous drug use. Geographic distribution of HTLV-1 and its confinement to a few well-defined ecosystems have yet to be explained. Diagnosis is now easy and can reduce transmission by intravenous drugs use. Development of a vaccine seems possible given the low genetic variability of this virus.