Screening transplant donors for HTLV-1 and -2.

Human T-cell leukemia virus-1 (HTLV-1) is the first pathogenic human retrovirus discovered in 1980. HTLV-1 causes 2 devastating diseases: adult T-cell leukemia/lymphoma (ATL) and a neurological disorder, HTLV-1–associated myelopathy/tropical spastic paraparesis (HAM/TSP or, more briefly, HAM). ATL becomes apparent in 2% to 5% of those infectedwithHTLV-1; another 1% to 2%will develop HAM. There are usually 2 to 3 decades of latency after the infection before the onset of symptoms. A second HTLV (HTLV-2) isolated in 1982 has been causally linked to HAM, but not ATL. In other cases, HTLV-1 and HTLV-2 infection may remain asymptomatic for years while being transmitted from person-toperson through host cells in body fluids and breast milk, blood cell transfusions, and solid organ transplantation. There are no licensed vaccines to prevent HTLV-1 or HTLV-2 infections.