There are six recognized members of the human herpes group of viruses. These include type 1 and type 2 herpes simplex viruses (HSV-1 and HSV-2), cytomegalovirus (CMV), Epstein-Barr virus (EBV), varicellazoster virus (VZV), and human herpes virus type 6 (HHV-6). These ubiquitous double-stranded DNA viruses are relatively large and lipid-enveloped. The capacity to induce a state of latency in the infected host has been proved for all of the herpes viruses. That is, after primary infection, the viruses remain forever with the host with the possibility for subsequent reactivations. The mechanisms of these reactivations are not understood completely. Both primary infections and recurrences may be associated with clinical illness or may be asymptomatic. To a large extent, the status of the host immune system determines the severity of the infection and the likelihood of recurrences. In general, infections are more severe and recurrences are more frequent in the most compromised hosts. This review focuses on HSV-1 and HSV-2, with emphasis on neonatal infections and maternal genital infections as a source of infection in the newborn.
The clinical illnesses caused by HSV-1 and HSV-2 are usually quite distinct. HSV-1 is the predominant cause of oral, ocular, and central nervous system infections occurring after the neonatal period, and HSV-2 is the predominant cause of genital and neonatal infections.
Evolutionary Origins of Human Herpes Simplex Viruses 1 and 2