(văr″ĭ-sĕl′ă)
[Pronunciation]
[L., a tiny spot]

An acute infectious disease, usually seen in children under age 15, caused by varicella-zoster virus.
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. 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.
SYN: chickenpox

Figure: VARICELLA (CHICKENPOX)




See: herpes zoster; varicella-zoster immune globulin

SYMPTOMS
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 pruritic (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, for example, when it occurs in adults or immunosuppressed children, chickenpox is complicated by superimposed bacterial pneumonia, encephalitis, or thrombocytopenia. Immunization with varicella vaccine provided during infancy is designed to prevent these complications.

ETIOLOGY
Chickenpox may strike individuals of any age who have not been previously been exposed to the virus. Epidemics are most frequent in winter and spring in temperate climates.

DIFFERENTIAL DIAGNOSIS
Impetigo, dermatitis herpetiformis, herpes zoster, and furunculosis may occasionally need to be distinguished from varicella, although usually the difference is obvious.

COMPLICATIONS
Secondary infections may occur, caused by scratching, which may result in abscess formation; at times, development of erysipelas or even septicemia may result. Occasionally, lesions in the vicinity of the larynx may cause edema of the glottis and threaten the life of the patient. Encephalitis is a rare complication. Varicella may be fatal in children with leukemia or children who are taking adrenocorticosteroids.

PREVENTION
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
Otherwise healthy affected children are treated with diphenhydramine or hydroxyzine to reduce itch and acetaminophen to reduce fever. Children at increased risk for complications and immunosuppressed adults are given varicella-zoster immune globulin as prophylaxis after exposure. If varicella infection develops in immunosuppressed persons or pregnant women in the third trimester, intravenous acyclovir is administered. Immunization with varicella vaccination is recommended for those children who have not had chickenpox and have not previously received the immunization.
See: Standard Precautions Appendix

Subentry:
varicella gangrenosa