Human herpesvirus type 6 and human herpesvirus type 7 infections of the central nervous system

In developing guidelines for the improved management of herpesvirus infections of the central nervous system (CNS), the International Herpes Management Forum (IHMF) has considered human herpesvirus (HHV) type 6 and type 7 disease. Although HHV-6 is generally asymptomatic, it has been associated with exanthema subitum, febrile convulsions and encephalitis in infants and immunocompromised adults and may play a role in multiple sclerosis, Guillain-Barre syndrome and acute disseminated encephalomyelitis. As HHV-6 is present in the brain tissue of healthy individuals, its role as an aetiological agent in CNS disorders is unclear. While polymerase chain reaction (PCR) is a method useful for diagnosis of other viral CNS infections, it has no value for diagnosing HHV-6. HHV-7 has not been shown to cause a specific disease but is associated with febrile convulsions and has been implicated as a cause of encephalitis. Ganciclovir and foscarnet, either alone or in combination, may be used for the management of HHV-6-related neurological disease. Although ganciclovir is unlikely to be effective against HHV-7-related CNS disease, foscarnet may be useful but prospective trials are needed.