Two types of human T-cell Leukemia Virus (HTLV) are known. They are also known as human T-cell lymphotrophic viruses. HTLV-1 often is carried by a person with no overt symptoms being apparent. However, HTLV-I is capable of causing a number of maladies. These include abnormalities of the T cells and B cells, a chronic infection of the myelin covering of nerves that causes a degeneration of the nervous system, sores on the skin, and an inflammation of the inside of the eye. HTLV-II infection usually does not produce any symptoms. However, in some people a cancer of the blood known as hairy cell leukemia can develop.

At one time there was a third HTLV virus. However, what once called HTLV-III is now referred to as the Human Immunodeficiency Virus (HIV). HIV is generally accepted to be the causative agent of...