HTLV-I/II prevalence in different geographic locations.

Human T-cell lymphotropic virus (HTLV) type I (HTLV-I) is the etiological agent of adult T-cell leukemia and HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-II is a closely related virus, and this infection is not clearly associated with clinical disease, although neurologic disorders are observed resembling HAM/TSP. Prevalence rates for HTLV-I infection in the general population are greater than 1% in the Caribbean Basin, Central Africa, and South Japan. In most other areas in the world, as far as we know, HTLV-I/II infections are mainly found in high-risk groups (ie, immigrants from endemic areas, their offspring, their sexual contacts and in patients and intravenous injection users attending sexually transmitted disease clinics). Also, a high rate of infection for both HTLV-I and HTLV-II infection was observed in the native Amerindian population in North America as well as South America. Blood donors are routinely screened for HTLV-I/II in North America, several countries in Europe, Japan, and Taiwan.