HHV-6 was discovered in 1986 by Dharam Ablashi, Robert Gallo and Zaki Salahuddin in the Laboratory of Tumor Cell Biology at the US National Cancer Institute. Originally called “human B lymphotropic virus (HBLV),” HHV-6 was first isolated from AIDS patients with cancer and lymphoproliferative disorders. In 1988, Koichi Yamanishi discovered that HHV-6B was the cause of exanthem subitum or roseola in infants. By the early 1990’s, it became clear that there were two distinct but closely related “variants” of HHV-6 (A & B). In 2011, the herpesvirus subcommittee of an international taxonomy group proposed that the variants be formally recognized as distinct viruses.