Human herpesvirus 6 in neurological diseases

Human herpesvirus 6 (HHV-6) is known since 1986 but the clinical disease exanthema subitum was described already in 1910. HHV-6 is a typical herpesvirus and also has the characteristic herpes group features, latency, tendency to reactivations, and neurotropism. In addition, it has an intriguing property to modulate immune response and to interact with other viruses, and alter their natural course. The spectrum of diseases associated with or caused by HHV-6 has been enlarging; especially neurological complications are increasingly reported. The diagnosis has proven problematic, both in regard to serology and molecular techniques. The two HHV-6 variants, A and B, differ in many respects. Due to encephalitis and chronic diseases, first of all MS, therapeutic regimens are needed. For these reasons, we have concentrated in HHV-6 already for years and reached small pieces of the viral behaviour.