Virological and clinical characteristics of human herpesvirus 6.

Six distinct human herpesviruses have been identified. They include Herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2), Cytomegalovirus (CMV), Varicella-zoster virus (VZV), Epstein-Barr virus and the recently described Human herpesvirus 6 (HHV-6). With the exception of HSV-2, the members of the family are ubiquitous and infect most of the human population in the first decade of life. HHV-6 possesses morphological and structural features characteristic of members from the herpesvirus family but it is both genetically and immunologically distinct from other members. The virus was first identified in 1986 by the group at the National Institutes of Health, Bethesda. Not until 1988 was the primary disease identified as that of a common childhood disease, exanthema subitum. There are independent reports on isolations of HHV-6 from the USA, Japan, U.K., Australia and Africa, demonstrating that the virus is a widespread agent. Its possible involvement in chronic fatigue disease and as a cofactor of development of AIDS are still subjects for discussion.