Human T-cell Lymphotropic Virus type I (HTLV-I) is a retrovirus that primarily infects T-cells, a type of white blood cell crucial for the immune system. It is transmitted through bodily fluids, including blood, breast milk, and sexual contact. HTLV-I is associated with several health conditions, including Adult T-cell Leukemia/Lymphoma (ATLL) and HTLV-I-associated myelopathy (HAM), which can lead to serious complications. Infection with HTLV-I is relatively common in certain regions, particularly in Japan, Caribbean countries, and parts of Africa. Many individuals infected with the virus remain asymptomatic for years, but some may develop symptoms later in life. There is currently no cure for HTLV-I, but early detection and monitoring can help manage associated health risks.