Chickenpox

Chickenpox - lesion on the leg	Chickenpox - lesions on the chest	Chickenpox, acute pneumonia - chest X-ray	Chickenpox - close-up

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 and risks  

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 a day of mild 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 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.

Prevention

Varicella zoster immune globulin (VZIG) may modify the severity of the disease, or prevent the disease if given within 96 hours after exposure to the virus. In general, this is reserved for high-risk individuals because the disease usually is benign. High risk individuals are those with no past history of chickenpox and who have a condition (such as depressed immune system, chemotherapy, AIDS, leukemia, lymphoma or organ transplant) and have been exposed to chickenpox.

Varicella vaccine is recommended between the ages of 12 and 18 months. (see immunization schedule) If a teenager is not known to have had Chicken pox, then blood can be drawn to see if he or she is susceptable to the disease, and if so the vaccine should be administered. Varicella vaccine has become a recommended childhood vaccine.

Symptoms 

• achy and feverish (one day prior to rash)
• a skin rash or lesion on the chest, back, shoulders, scalp, or other areas
• lesions on the mouth, vagina, rectum, eye, or other mucus membranes
• the rash changes over several hours to fluid-filled blisters
• crusting, after the blister breaks, occurs two to four days
• crusts become progressively darker with time
• scabs fall off in about nine to 13 days
• itching, may be severe

Signs and tests

The appearance of the rash is sufficient to establish the diagnosis.

Treatment   

General measures to relieve itching associated with skin lesions include cool water soaks or compresses, and bathing with one cup of baking soda added to a bathtub of lukewarm water. Topical preparations such as nonprescription calamine lotion, antihistamines, or other lotions containing camphor, menthol or phenol 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, use acetaminophen instead of aspirin. Aspirin use during a viral illness, particularly chickenpox, has been associated with a risk of developing Reye’s syndrome. A sedative given at night may be prescribed for sleep.

The prescription drug acyclovir has been approved by the FDA for use in treating the symptoms of chicken pox in people over 2 years old. Although acyclovir usually is reserved for teenagers, because the disease is more severe in that age group. The drug should help reduce the severity of chickenpox symptoms, especially in older children and teenagers if taken within 24 hours of the rash’s first appearance. It may also be prescribed in severe cases or in people who are immunosuppressed. An alternative antiviral agent is vidarabine.

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.

Prognosis

The outcome is expected to be excellent in an uncomplicated case. Chickenpox encephalitis, a rare complication of chickenpox, generally has a poor outcome.