Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Human T-cell leukemia virus type 1 ?
    ### Response:
    Human T-cell leukemia virus, type 1 (HTLV-1) is a retroviral infection that affect the T cells (a type of white blood cell). Although this virus generally causes no signs or symptoms, some affected people may later develop adult T-cell leukemia (ATL), HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) or other medical conditions.
    