Bisexual men with AIDS instead of AIDS patients with hemophilad or intravenous drug users further support the existence of an infectious cofactor (Beral et al., 1990). According to the epidemiological data, several groups set out to identify a "KS agent" in the early 1990s. In 1994, Chang and Moore's group successfully identified the infectious cause of KS as a new herpesvirus called Kaposi's sarc