Herpesvirus Infections

The herpes group of viruses is composed of at least eight human viruses and numerous animal viruses. The human herpesviruses include herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human herpesvirus types 6 (HHV-6), 7 (HHV-7), and 8 (HHV-8, also known as Kaposi sarcoma–associated herpesvirus). Human herpesviruses share the properties of latency and reactivation. Members of the group can cause productive lytic infections, in which infectious virus is produced and cells are killed, or nonproductive lytic infections, in which viral DNA persists but complete replication does not occur and cells survive. After acute lytic infections, herpesviruses often persist in a latent form for years; periodic reactivations are followed by recurrent lytic infections. Sites of latency vary: HSV and VZV persist in neural ganglion cells, EBV persists in B cells, and CMV probably remains latent in many cell types. The sites of latency for HHV-6 and HHV-7 have not been identified, although both herpesviruses have been detected in salivary glands. All human herpesviruses have a worldwide distribution. Considerable eff