A variety of retrovirus, also known as the human T-cell leukemia virus or HTLV, exists in several forms. The most prevalent type is HTLV-1, which is commonly found in tropical regions such as southern Japan, the Caribbean, South America, and West Africa. The transmission of the virus can occur through sexual contact, breastfeeding, receiving a transfusion of infected blood, or among intravenous drug users who share contaminated needles.
While most people infected with HTLV-1 do not exhibit any symptoms, a small percentage (fewer than one in 20) may develop severe health conditions. One such condition is the cancerous disease known as adult T-cell leukemia, which can manifest up to 20 years post-infection. This disease is characterized by a swift and abnormal proliferation of white blood cells in the bone marrow and cells in the lymphoid tissue. It often results in the enlargement of lymph nodes, liver, and spleen. Anti-cancer medications may temporarily halt the disease by eliminating abnormal cells, but the typical survival duration ranges from only a few months to a few years.
Another health issue related to HTLV-1 infection is myelopathy, a disease affecting the spinal cord. This condition leads to pain in the lower back and legs, accompanied by an increasingly severe weakness in the legs and challenges with walking.