Clinical Information

Human herpesvirus-6 (HHV-6) is a member of the Herpesviridae family. These DNA viruses contain a capsid surrounded by a lipid envelope. Among members of this group, this virus is most closely related to cytomegalovirus (CMV) and HHV-7. As with other members of the herpesvirus group (herpes simplex virus [HSV]-1, HSV-2, varicella-zoster virus, CMV, Epstein-Barr virus, HHV-7, HHV-8), HHV-6 may cause primary and reactivated infections.(1) Infection with HHV-6 occurs early in childhood. Most adults (80%-90%) have been infected with this virus.

Human herpesvirus-6 was first linked with exanthem subitum (roseola infantum) in 1998; since then, the virus has been associated with central nervous system disease almost exclusively in patients who are immunocompromised.(1) HHV-6 is commonly detected in patients post transplantation. Clinical symptoms associated with this viral infection include febrile illness, pneumonitis, hepatitis, and encephalitis. However, most HHV-6 infections are asymptomatic.(2)

Human herpesvirus-6 is designated as variant A (HHV-6A) or variant B (HHV-6B) depending on restriction enzyme digestion patterns and its reaction with monoclonal antibodies. Generally, variant B has been associated with exanthem subitum, whereas variant A has been found in many immunosuppressed patients.(3) Infection with HHV-6 is very common, approaching 100% seroprevalence in developed countries.(4) In about 1% of the population, HHV-6 can integrate into the host genome. Often asymptomatic in immunocompetent hosts, reactivation can cause serious disease in immunocompromised individuals, particularly those with AIDS and transplant recipients, which can cause rejection of the transplanted organ and even death.(1)

This assay will be used to assist with diagnosis and monitoring of HHV-6 disease in patients who are suspected of having disease due to HHV-6 infection. It will also be used as an initial indicator of infection versus chromosomally-integrated HHV-6.