(var″ĭ-sel′ă) [variola + L. diminutive suffix--cella] An acute infectious disease, usually seen in children under age 15, caused by varicella-zoster virus, and one of the classic diseases of childhood. SYN: chickenpox. SEE: illus.; herpes zoster; varicella-zoster immune globulin.
INCIDENCE: Chickenpox is endemic worldwide. Most children acquire the disease during the winter and spring, most likely from other schoolchildren. Epidemics are most frequent in winter and spring in temperate climates.
CAUSES: It is transmitted mainly by respiratory droplets that contain infectious particles; direct contact with a lesion and contaminated equipment also can spread the virus. Reactivation of the virus in adults causes shingles. Varicella may strike people of any age who have not been previously been exposed to the virus.
SYMPTOMS AND SIGNS: Its hallmark is a rash, described clinically as having a "dewdrop on a rose petal" pattern, scattered in clusters (crops) over the trunk, face, scalp, upper extremities, and sometimes the thighs. After an incubation period of 2 to 3 weeks (usually 13 to 17 days), patients develop fever, malaise, anorexia, and lymphadenopathy, followed by the appearance of an extremely itchy rash that starts flat and, over time, becomes a small blister on a red base, and then eventually forms crusted scabs. All three stages of the rash may be present on the body at one time. Varicella may be transmitted to others until all lesions are crusted over.
Occasionally when varicella occurs in adults or immunosuppressed children, it is complicated by superimposed bacterial pneumonia, encephalitis, or thrombocytopenia.
DIAGNOSIS: Impetigo, dermatitis herpetiformis, herpes zoster, and furunculosis occasionally must be distinguished from varicella, although usually the difference is obvious.
PREVENTION: Immunization with varicella vaccine provided during infancy is designed to prevent these complications. Administration of varicella-zoster immune globulin (VZIg) within 72 hr of exposure will prevent clinical varicella in susceptible, healthy children. The following conditions should alert one to the possible need for use of VZIg: immunocompromised children; newborns of mothers who develop varicella in the period 5 days before to 48 hr after delivery; postnatal exposure of newborns (esp. those who are premature) to varicella; healthy adults who are susceptible to varicella and who have been exposed; pregnant women who have no history of having had varicella and who have had significant exposure. The use of VZIg in pregnant women will not prevent fetal infection or congenital varicella syndrome. Live attenuated vaccine is now available for general use.
Because severe illness and death have resulted from varicella in children being treated with corticosteroids, these children should avoid exposure to varicella.
TREATMENT: Affected children who are otherwise healthy are treated with diphenhydramine or ...