Human T-cell lymphotropic virus type 1 prevalence estimates are usually based on serological screening of blood donors, pregnant women, and other selected population groups. Previously, data on the global epidemiology of human T-cell lymphotropic virus type 1 infection have been summarized unsystematically and without a focus on general populations. To assess the implications of the virus for healthcare systems it is essential to know its past and present prevalence. The widely cited estimate that 10-20 million people are infected with human T-cell lymphotropic virus type 1 worldwide was calculated from data that are now 25 years old. This estimate may therefore no longer reflect the global epidemiology. The objective of this study was to collate published data that are truly representative of the general population through a systematic review of the literature. Fifty-nine relevant studies were identified and the 17 that met the inclusion criteria were all cross-sectional designs; none reported incidence. The prevalence of human T-cell lymphotropic virus type 1 was highest in the two studies of Japanese islands (36.4%; 95% CI: 29.9-42.8) and lowest in studies from Mongolia, Malaysia and India. In Haiti the prevalence was 3.8% (95% CI: 1.78-5.86); in Africa between 6.6% (95% CI: 4.0-9.9) and 8.5% (95% CI: 6.99-10.10) in Gabon, and 1.05% (95% CI: 0.63-1.47) in Guinea. Only three studies were from West Africa and none were from the South; the only study from India was from the north of the country. We conclude that there is a paucity of general population data from countries in which human T-cell lymphotropic virus type 1 is endemic, and that new studies are required to reevaluate the global burden of infection.
A serological investigation for human T cell leukemia virus I (HTLV-I) infection was carried out at the University Hospital, Kuala Lumpur. A total of 626 sera from a non-patient population and 1,038 sera from unselected in-patients were screened for HTLV-I antibodies using an enzyme-linked immunosorbent assay (ELISA). 27/1664 (1.6%) were found to be reactive. However, on Western blotting, only 2 sera were confirmed positive, both showing reactions for the major core (p19 and p24) and the envelope (gp46) proteins. Both of the serum samples were from unselected hospital patients. Most of the remaining sera which were reactive on screening showed indeterminate results on Western blotting. These were further tested by radioimmunoprecipitation assay (RIPA) and none of these sera gave a positive reaction. Therefore, only 2/1038 (0.19%) unselected patients could be confirmed to have antibodies to HTLV-I. None of the normal individuals screened showed a positive Western blot result. Our data indicate that HTLV-I infection is present in our population, but at a low prevalence rate.