Contributor: Gordon K. Klintworth
Varicella (chickenpox) is a common viral infection. It is a common highly contagious viral systemic infection caused by the varicella-zoster virus. It is the primary infection of this viral disease. Infection is usually acquired during childhood. The predominant clinical manifestation is a generalized vesicular eruption of  the skin. After an incubation period (11-21 days) fever malaise and a pruritic rash develop. The rash begins as a maculopapular eruption and the lesions rapidly become vesicles and then pustules. Because the skin lesions appear in crops they are present in various stages of evolution at the same time within a particular area. The mucous membranes and particularly the oral mucosa may also be affected. In varicella lesions may develop on the margins of the eyelids, conjunctiva, or corneoscleral limbus. Chickenpox is spread mainly via the respiratory route, but it can also occur by direct contact with the cutaneous vesicles. The initial infection is believe to start in the respiratory respiratory epithelium and perhaps the conjunctival epithelium. During the primary infection the virus becomes latent within perineural satellite cells of the dorsal root ganglia. Later in life the latent virus may become activated leading to herpes zoster. An extremely virulent infection can develop in a patient with an immunodeficiency state, such as AIDS.