Incidence of adult T-cell leukemia/lymphoma in nonendemic areas.

Adult T-cell leukemia/lymphoma (ATLL) is a mature T-cell neoplasm with extremely poor prognosis caused by human T-cell leukemia virus type 1 (HTLV-1). The distribution of HTLV-1 and the incidence of ATLL in endemic areas have been well described, however, little is known about the incidences and the trends of the disease in nonendemic areas. Recently, studies have shown that the HTLV-1 carriers are increasing in nonendemic areas. Also, the incidence of ATLL seems to be significantly increasing in nonendemic areas suggesting that HTLV-1 carriers have emigrated from endemic areas. These epidemiologic studies indicate the necessity of edification of the disease caused by HTLV-1 and establishing appropriate preventive methods against infection in nonendemic areas.