Although no disease syndrome has been definitively linked with HTLV-II, HTLV-I is known to be the etiologic agent of both adult T cell leukemia/lymphoma and a neurologic syndrome identified as tropical spastic paraparesis/HTLV-associated myelopathy. One population especially at risk is intravenous drug users, among whom the incidence of HIV infection continues to increase, and in certain populations of intravenous drug users, HTLV-II appears endemic. An increasing number of people are being exposed to the two known pathogenic human retroviruses: the human immunodeficiency virus (HIV) and the human T cell leukemia/lymphoma viruses (HTLVs).
