T-cell lymphotropic virus type 1 (HTLV-1) is a type of virus that primarily infects T-cells, a crucial part of the immune system. It is classified as a retrovirus, meaning it can integrate its genetic material into the host's DNA. HTLV-1 is mainly transmitted through sexual contact, blood transfusions, and from mother to child during childbirth or breastfeeding. Infection with HTLV-1 can lead to various health issues, including adult T-cell leukemia/lymphoma (ATLL) and HTLV-1-associated myelopathy (HAM). Many people infected with the virus may remain asymptomatic for years, but some may develop serious conditions later in life. There is currently no cure for HTLV-1, but early detection and monitoring can help manage symptoms.