Human herpes virus 6, a member of the B-herpes virus subfamily, was initially identified in 1986 in AIDS and lymphoproliferative disease patients. HHV6 infection is widespread, with seroprevalence approaching 100 percent. Infection with HHV-6 in children causes the sixth disease, also known as roseola infantum.

Just like any other member of the herpesviridae family, HHV-6 establishes latency in the host. The virus hides in lymphocytes and monocytes and could maintain a low replication level throughout life. It is often secreted in saliva and can be an opportunist in immunocompromised patients or transplant recipients. There is a growing body of evidence indicating a strong correlation between HHV-6 and multiple sclerosis (MS). The virus has been isolated from brain lesions from MS patients. The virus has also been implicated in patients with febrile seizures and several investigators have shown that antiviral therapy can improve prognosis in MS patients.

HHV6 infections can be diagnosed using culture or serological methods. These methods are more time consuming and may lack the specificity and sensitivity that molecular testing provides. In addition, serological tests provide only retrospective information of an HHV6 exposure. PCR detection is a rapid, sensitive and highly specific method of detection.