Varicella-zoster virus, an ubiquitous human pathogen, causes vesicular rash during varicella, the primary infection of the host and zoster corresponding to reactivation. The symptoms could be various, nervous systems and lung being involved. Usually mild, varicella could be severe in immunocompromised patients, during pregnancy for the mother and the foetus, for the newborn and also for adults. Post herpetic neuralgia in old patient is the main complication of zoster. Various methods for virological diagnosis (culture, cytology, serology, PCR) with different sensibilities and specificities depending mainly of sample type are available. Various antiviral drugs are available, acyclovir being the reference one.