Natural history of varicella zoster virus.

The varicella zoster virus (VZV) is a herpesvirus responsible for two distinct clinical disorders, primary varicella (chickenpox) and zoster (shingles). Primary varicella is a common childhood disease in Western countries, which presents as pruritic macules, papules, vesicles, pustules, and crusts, usually on the back, chest, face, and abdomen. In immunocompetent children, chickenpox is generally a mild disease with little morbidity and rare mortality. Primary varicella is associated with more morbidity in adults. Following resolution of primary varicella, VZV persists in a latent form in dorsal ganglion cells for what is usually an extended period of time. For reasons that are still poorly understood, VZV can later start replicating in the ganglion, producing severe neuralgia and spread of the virus down the sensory nerve. Vesicles then appear on the skin in the distribution of this nerve, producing the characteristic dermatomal rash of shingles. The vesicles progress to pustules, then to crusts that eventually are lost. Scarring and changes in pigmentation can result, but the most frequent sequela of zoster is postherpetic neuralgia, which is usually most severe in the elderly. Primary varicella or herpes zoster in immunocompromised patients can sometimes involve internal organs (eg, lungs, liver, brain) resulting in high rates of morbidity and mortality. Congenital VZV infection is uncommon but can result in severe congenital malformations. A Tzanck smear can be useful to demonstrate a herpesvirus infection, but confirmation of VZV as the cause of the infection requires at least one of the following tests: culture, serology, direct immunofluorescence staining, or molecular techniques.