Chickenpox is a highly contagious, usually mild childhood disease caused by varicella-zoster virus, which also causes herpes zoster ( shingles ) in adults.

Alternative Names

Varicella

Causes, incidence, and risk factors

Chickenpox is a viral disease characterized by itching and a skin rash with fluid-filled blisters that burst and form crusts. The onset of the chickenpox rash may be preceded by fever and general 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 itself seldom causes scarring. However, chickenpox lesions can become infected, often due to vigorous scratching. Some of these secondary infections may be severe enough to require hospitalization. Chickenpox is spread from person-to-person by contact with infected respiratory droplets, or by contact with articles freshly soiled by discharge from the lesions. It is contagious from two days before the onset of the rash, 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 vaccinated or previously infected. 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.

Signs and tests

The appearance of the rash is generally sufficient to establish the diagnosis. If confirmation is required, a sample of fluid from a lesion may be examined under a microscope, or blood tests may be performed.

Treatment

General measures to relieve itching associated with skin lesions include cool water soaks or compresses. Some over-the-counter creams may be helpful. Fingernails should be trimmed to prevent scratching, which may lead to a secondary infection . Infant's hands may be covered with a soft cotton or flannel mitten to prevent scratching (the hand should never be restrained). DO NOT USE ASPIRIN! To reduce fever and relieve pain, use acetaminophen instead. Aspirin use during a viral illness, particularly chickenpox, has been associated with a risk of developing Reye's syndrome . The prescription drug Acyclovir may be recommended by your doctor, but is generally used only in children with altered immune systems or those at high risk for serious complications. Children should be kept home from school or day-care until all of the blisters have broken and scabbed over, and they feel well enough to participate in normal activities.

Expectations (prognosis)

The outcome is generally excellent in uncomplicated cases. Encephalitis, pneumonia, and other invasive bacterial infections are serious, but rare, complications of chickenpox.

Complications

Calling your health care provider

Call your health care provider if you think that your child has chickenpox or if your child is over 12 months of age and has not been vaccinated against chickenpox.

Prevention

Varicella vaccine is recommended as a routine immunization for children 12 months and older. In some children at high risk for complications of chickenpox, varicella vaccine or varicella zoster immune globulin (VZIG) may prevent or improve the recovery from the disease if given shortly after exposure -- talk to your doctor if your child has been exposed.