Human herpesvirus 6: A herpes virus that apparently lies dormant in many people, human herpesvirus 6 is most likely to cause problems when the immune system is compromised by disease, as in AIDS patients, or by deliberate immune suppression, as in organ transplant patients. There are two forms of HHV-6, A and B. A is rare, and acquired in adulthood. B is relatively common, usually acquired in childhood, and associated with roseola. Both A and B can reactivate at a later date, and are believed to contribute to diseases of the bone marrow and/or central nervous system in some patients, including fatal encephalitis, chronic fatigue syndrome, and possibly multiple sclerosis. Diagnosis is by rapid blood culture or other blood test. Treatment is experimental at this time, but anti-viral drugs or beta interferon may be tried. Abbreviated HHV-6.
See also roseola.