The type species of roseolovirus isolated from patients with AIDS and other lymphoproliferative disorders. It infects and replicates in fresh and established lines of hematopoietic cells and cells of neural origin. It also appears to alter NK cell activity. HHV-6; (HBLV) antibodies are elevated in patients with AIDS, sjogren's syndrome, sarcoidosis, chronic fatigue syndrome, and certain malignancies. HHV-6 is the cause of exanthema subitum and has been implicated in encephalitis.