Human herpesvirus 6

The development of techniques for the culture of lymphoid cells and the iso lation of viruses that infect these cells led to the discovery of human her pesvirus (HHV) 6 in 1986. At the time, HHV-6 was the first new human herpes virus to be discovered in roughly a quarter of a century, and its isolation marked the beginning of an era of discovery in herpesvirology, with the id entification of HHV-7 and HHV-8 (Kaposi's sarcoma-associated herpesvirus) d uring the following decade. Like most human herpesviruses, HHV-6 is ubiquit ous and capable of establishing a lifelong, latent infection of its host. H HV-6 is particularly efficient at infecting infants and young children, and primary infection with the virus is associated with roseola infantum (exan them subitum) and, most commonly, an undifferentiated febrile illness. Vira l reactivation in the immunocompromised host has been linked to a variety o f diseases, including encephalitis, and HHV-6 has been tentatively associat ed with multiple sclerosis. This article discusses the major properties of HHV-6, its association with human disease, and the pathobiological signific ance of viral reactivation.