The human T-cell lymphotropic viruses type I and II (HTLV-I and HTLV-II) are retroviruses that are more common in parts of southern Japan and certain Pacific Islands; sub-Saharan Africa; and the Caribbean basin, Central and South America. In Europe and North America, HTLV II is found most commonly in intravenous drug users. These viruses are not related to HIV.

Most HTLV-I infected individuals remain healthy and never develop any symptoms. However, two to four per cent of people infected with HTLV-I develop an adult T-cell leukemia/lymphoma (ATL), a rare cancer of the blood. Other rare diseases associate with HTLV 1 are myelopathy (a neurological disorder affecting the muscles of the legs) or B-cell chronic lymphocyte leukemia. HTLV-II typically is asymptomatic, but in some cases hairy-cell leukemia, a rare cancer of the blood, may occur.

The HTLV viruses can be transmitted by exposure to blood or sexual contact (predominantly male-to-female), and can be passed from mother to child through breast milk. HTLV I and II remain in the body life-long, however, ATL can be prevented if diagnosed and treated in its early stages.

Canadian Blood Services tests every blood donation for HTLV using an antibody test that detects the body’s immune response to the virus. Only blood that passes the test is distributed to hospitals