Varicella

Varicella, also known as chicken pox, is an intraepidermal vesicular eruption caused by the varicella-zoster virus, a herpes virus. It appears as a generalized vesicular eruption. Varicella is primarily a disease of childhood, and it is highly contagious. Following exposure, there is a two to three week incubation period, which is followed by a several day prodrome of headache, fever, chills, sore throat, malaise, and cry cough. The characteristic eruption follows. The lesions mostly affect the trunk, but can also be found on the face, extremities, palms and soles, and mucous membranes. The lesions emerge in "crops", which rapidly evolve over eight to twelve hours, progressing from macule to vesicle and pustules. This is followed over several days by crusting and, ultimately, healing. The rash is extremely pruritic (itchy). Important characteristics of the rash are: all stages of the lesion are present at the same time (macules, vesicles, and pustules); each vesicle appears as "a dewdrop on a rose petal"—a 2-3 mm vesicle on an erythematous base. The incidence of varicella has plummeted in recent years due to the introduction of vaccination with a live attenuated virus.

With what can it be confused?

With the emergence of the threat of bioterrorism, smallpox is once again in the differential diagnosis. One of the key distinguishing features is that in smallpox all of the lesions are at a uniform stage of development, whereas in varicella all stages are simultaneously present. Other possibilities in the differential diagnosis are coxsackievirus, disseminated herpes simplex, and ricketsial pox.

How is it diagnosed?

The diagnosis of varicella is usually made clinically. A Tzanck preparation will reveal multinucleated giant cells, as is the case in other herpes virus infections. Direct immunofluorescence of vesicle contents are rarely necessary. Viral culture is difficult and not a preferred diagnostic.

How is it treated?

Alleviation of symptoms is the mainstay of varicella therapy. Itching can be reduced with oral antihistamines (e.g. diphenhydramine or hydroxyzine) and topical agents such as calamine lotion. Oatmeal baths (e.g. Aveeno) are helpful. Immunosuppressed patients and adults should be treated with acyclovir (Zovirax), to reduce the incidence of complications. In children, aspirin should be avoided due to the risk of developing Reye's syndrome. Vaccination with a live attenuated strain can be used for primary prevention. Varicella Zoster Immune Globulin (VZIG) is used for post-exposure prophylaxis in certain cases, such as immunocompromised individuals, and neonates born to exposed mothers.

What is the prognosis

The patient is infectious from one to two days before the rash comes out until the lesions have crusted over, typically four to five days. The risk of developing major complications, specifically encephalitis, pneumonia, and hepatitis, is higher in adults and in the very young.

Date created 04/11/2007

Last updated 01/03/2009