NEWLY DISCOVERED HUMAN HERPESVIRUSES (HHV-6 AND HHV-7)

Human herpesvirus (HHV)-6 and HHV-7 are lymphotropic beta-herpesviruses which infect almost all individuals during infancy and persist lifelong. Two genetically distinct variants of HHV-6, HHV-6A and HHV-6B, have been described and the latter has been shown to be a common cause of febrile childhood illness, including roseola (Exanthem subitum). The pathogenesis of infection by HHV-6 and HHV-7 remains uncertain, but is an area of active research interest. This review describes the current status of research on HHV-6 and HHV-7 and draws attention to the unique biologic and molecular biologic properties which distinguish these agents from other herpesviruses.