Varicella-zoster virus (VZV) infection causes two clinically distinct forms of disease. Primary infection with VZV results in varicella (chickenpox), characterized by vesicular lesions in different stages of development on the face, trunk, and extremities. Herpes zoster, also known as "shingles", results from reactivation of endogenous latent VZV infection within the sensory ganglia. This clinical form of the disease is characterized by a painful, unilateral vesicular eruption, which usually occurs in a restricted dermatomal distribution.
The diagnosis of these two diseases is usually made clinically. However, the use of diagnostic assays may be important in specific situations, as discussed below.
The clinical manifestations of chickenpox and shingles are discussed elsewhere. (See "Treatment of herpes zoster in the immunocompetent host" and "Clinical features of varicella-zoster virus infection: Chickenpox" and "Clinical manifestations of varicella-zoster virus infection: Herpes zoster".)
The diagnosis of VZV infection is usually a clinical diagnosis based on the characteristic vesicular lesions, which are seen widespread in chickenpox (varicella) or in a restricted dermatomal pattern with associated neuritis in shingles (herpes zoster).
However, additional diagnostic information may be useful in the following situations: