Chickenpox

Alternative names:

varicella

Definition:

A highly contagious, usually mild childhood disease caused by the Herpes virus varicella-zoster virus, which also causes herpes zoster (shingles).

Causes, incidence, and risk factors:

Chickenpox is a viral disease characterized by itching (pruritus) and a skin rash with fluid-filled blisters that burst and form crusts. The onset of the chickenpox rash may be preceded by a day of mild fever and malaise. The rash begins with a few small reddish bumps (papules) that quickly fill with fluid to form small blisters (vesicles). The vesicles appear in "crops", small groupings, first on the trunk then spreading to the extremities, face and scalp over a period of two to four days. The rash may spread into the mouth and other internal parts of the body. The vesicles break and a light brown scab or crust forms over the top. This crust gradually darkens to a dark brown before it finally falls off, usually within two weeks of the onset of the illness.

Chickenpox seldom causes scarring, but when it does, the scars most often occur around the eyes and consist of a small depression. Chickenpox lesions can become infected, usually from scratching and most frequently with staphylococcus. These secondary infections may be severe enough to require hospitalization.

Chickenpox is spread from person to person by respiratory droplets, or by contact with articles freshly soiled by discharge from the lesions. It is contagious two days before the onset of the rash until six days after the appearance of the first lesions, or until all of the lesions are crusted over. The incubation period is 10 to 21 days. There is universal susceptibility to the virus in those not previously infected. Most children have been infected with the virus by the age of 10. After infection, lifelong immunity against recurrent infection is usually present. However, a person with a history of chickenpox may develop shingles (herpes zoster) later in life.