The incubation period of varicella is generally 14 to 16 days, witha range of 10 to 21 days after exposure. Prodromal symptomsof fever, malaise, and anorexia may precede the rash by 1 day.The characteristic rash appears initially as small red papules thatrapidly progress to nonumbilicated, oval, “teardrop” vesicles onan erythematous base. The fluid progresses from clear to cloudy,and the vesicles ulcerate, crust, and heal. New crops appear for 3to 4 days, usually beginning on the trunk followed by the head,the face, and, less commonly, the extremities. There may be atotal of 100 to 500 lesions, with all forms of lesions being presentat the same time. Pruritus is universal and marked. Lesions maybe present on mucous membranes. Lymphadenopathy may begeneralized. The severity of the rash varies, as do systemic signsand fever, which generally abate after 3 to 4 days.
The preeruption phase of zoster includes intense localized and constant pain and tenderness (acute neuritis) along a dermatome, accompanied by malaise and fever. In several days,the eruption of papules, which quickly vesiculate, occurs in thedermatome or in two adjacent dermatomes. Groups of lesions occur for 1 to 7 days and then progress to crusting and healing.Thoracic and lumbar regions are typically involved. Lesionsgenerally are unilateral and are accompanied by regionallymphadenopathy. In one third of patients, a few vesicles occuroutside of the primary dermatome. Any branch of cranial nerveV may be involved, which also may cause corneal and intraorallesions. Involvement of cranial nerve VII may result in facialparalysis and ear canal vesicles (Ramsay Hunt syndrome).Ophthalmic zoster may be associated with ipsilateral cerebralangiitis and stroke. Immunocompromised persons may haveunusually severe, painful herpes zoster that involves cutaneousand, rarely, visceral dissemination (to liver, lungs, and centralnervous system). Postherpetic neuralgia, defined as pain persisting longer than 1 month, is uncommon in children.
Laboratory testing confirmation for diagnosis is usuallyunnecessary. PCR is the current diagnostic method of choice,and genotyping to distinguish vaccine and wild-type strainsis available through the CDC. Detection of varicella-specificantigen in vesicular fluid by immunofluorescence using monoclonal antibodies or demonstration of a fourfold antibodyincrease of acute and convalescent sera is also diagnostic but not as sensitive as PCR.
The diagnosis of varicella and zoster is based on the distinctive characteristics of the rash. Eczema herpeticum, or Kaposi varicelliform eruption, is a localized, vesicular eruption caused by HSV that develops on skin affected by underlying eczema or trauma. The differentiation between zoster and HSV infection may be difficult because HSV may cause eruption that appears to be in a dermatomal distribution. Coxsackievirus A infection has a vesiculopustular appearance, but lesions are usually localized to the extremities and oropharynx. A previously healthy patient with more than one recurrence probably has HSV infection, which can be confirmed by viral culture.