A type of herpesvirus that causes Kaposi sarcoma. Kaposi sarcoma herpesvirus (KSHV) is primarily transmitted through genital fluids and saliva. Most people infected with KSHV do not develop Kaposi sarcoma. In people with weakened immune systems, including people with HIV, the viral infection is much more likely to advance to Kaposi sarcoma than in people with healthy immune systems.