Kaposi's sarcoma (KS) is an AIDS-defining condition caused by the human herpesvirus 8 (HHV-8). HHV-8, also known as Kaposi's sarcoma-associated herpesvirus (KSHV), is a virus that can be transmitted through various routes, including sexual contact and blood, as well as organ or tissue transplants. HHV-8 is thought to be the primary cause of the development of KS, but other factors, such as weakened immunity, may play a role in its progression. KS can also be caused by some types of chemotherapy, radiation, or other treatments. Treatment for KS typically includes antiviral drugs, chemotherapy, and radiation. Surgery may be necessary in some cases. Early diagnosis and treatment are important for successful management of KS.