Although human T-lymphotropic virus type I (HTLV-I) was the first human retrovirus to be isolated and the first to be shown to cause a human cancer, adult T-cell leukaemia/lymphoma (ATLL), its importance was overshadowed by the isolation and identification of human immunodeficiency virus as the cause of the acquired immunodeficiency syndrome. A resurgence of interest in HTLV-I, a member of the oncovirinae subfamily of the family Retroviridae, occurred after the fortuitous discovery that patients with endemic tropical spastic paraparesis (TSP) in Martinique had serological evidence of HTLV-I infection (Gessain et al., 1985). Confirmatory data demonstrating IgG antibodies against HTLV-I in sera and cerebrospinal fluids (CSF) of patients with TSP were soon reported from Jamaica (Rodgers-Johnson et al., 1985, 1988), Colombia (Rodgers-Johnson et al., 1985; Zaninovic, 1987), Trinidad (Bartholomew et al., 1986), the Seychelle Islands (Roman et al, 1987) and West Africa (Gessain et al., 1986; Tournier-Lasserve et al., 1987). In addition, patients with a TSP-like disease in southern Japan, designated HTLV-I-associated myelopathy (HAM) (Osame et al., 1987), were found to be infected with HTLV-I. TSP and HAM are now known to represent the same clinical syndrome and are collectively called TSP/HAM, although the term HTLV-I myeloneuropathy seems more appropriate (Rodgers-Johnson et al., 1990).
Since 1983, we have intensified our search for high-prevalence foci of HTLV-I infection, concentrating primarily on isolated populations of the western Pacific.