THE RISK OF DEVELOPMENT OF HTLV-I-ASSOCIATED MYELOPATHY TROPICAL SPASTIC PARAPARESIS AMONG PERSONS INFECTED WITH HTLV-I

  • 1 January 1990
    • journal article
    • research article
    • Vol. 3  (11) , 1096-1101
Abstract
Using data obtained in national surveys of human T-lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM-TSP) conducted in Japan in 1987 and 1988, we estimated the yearly and lifetime risk that HAM/TSP will develop in an HTLV-I-infected person. "Definite" HAM-TSP was defined as slowly progressive meylopathy with antibodies to HTLV-I in both serum and cerebrospinal fluid. Estimates of HTLV-I infection rates in eight endemic prefectures, by age group and sex, were obtained from serologic studies of blood donors; population figures, by age group, sex, and prefecture, were obtained from the census. Of 589 definite cases of HAM/TSP reported nationally, 397 occurred in residents of the eight endemic prefectures; of these, 170 reported onset of illness during the years 1982-1988 (average incidence, 24.3 cases/year). Using the estimated HTLV-I infection rates and the 1985 census figures, we estimated the number of HTLV-I-infected persons in the eight prefectures in 1985 at 794,800. We therefore estimated the incidence of HAM/TSP among HTLV-I-infected persons at 3.1 .times. 10-5 cases/year; assuming a lifetime of 75 years, the lifetime incidence is approximately one quarter of 1%. This estimate is important in counseling persons such as blood donors found to be infected with HTLV-I.