A type of virus that causes Kaposi sarcoma (a rare cancer in which lesions grow in the skin, lymph nodes, lining of the mouth, nose, and throat, and other tissues of the body). Human herpesvirus 8 also causes certain types of lymphoma (cancer that begins in cells of the immune system). Also called HHV8, Kaposi sarcoma-associated herpesvirus, and KSHV.