Université de Liège, laboratoire de virologie fondamentale et d’immunologie virale, Pathologie B23, 4000 Liège, Belgique
Varicella Zoster virus (VZV) is an alphaherpesvirus responsible for two well-known pathologies. It is indeed the etiological agent of varicella (chickenpox), a childhood infection and zoster (shingles) which results from the reactivation of the virus remained latent in sensory ganglia. Only eight of the 120 Herpesviruses described so far, among which VZV and Herpes Simplex type-1 and type 2 (HSV-1, -2), are able to infect humans. For many years, HSV-1, which has been extensively studied has been considered as the prototype of this family. Nevertheless, data accumulated over the last 15 years tend to demonstrate that VZV is quite different from its cousin, particularly concerning the mechanisms that control latency. Epidemiological data confirm the differences between these two viruses : in our temperate countries, VZV infects very young children and zoster, usually observed only once is more frequent in the elderly. On the contrary, primary infections due to HSV-1 happen later and reactivations episodes are numerous and decrease with age. A better understanding of the VZV biology has allowed to develop efficacious antiviral compounds and to produce a vaccine whose efficacy has been demonstrated in the United States where a universal varicella vaccination program has started 10 years ago.