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Chickenpox

Definition

Chickenpox is one of the classic childhood diseases. A child or adult with chickenpox may develop hundreds of itchy, fluid-filled blisters that burst and form crusts. Chickenpox is caused by a virus.

The virus that causes chickenpox is varicella-zoster, a member of the herpesvirus family. The same virus also causes herpes zoster (shingles) in adults.

Alternative Names

Varicella; Chicken pox

Causes, incidence, and risk factors

In a typical scenario, a young child is covered in pox and out of school for a week. The first half of the week the child feels miserable from intense itching; the second half from boredom. Since the introduction of the chickenpox vaccine, classic chickenpox is much less common.

Chickenpox can be spread very easily to others. You may get chickenpox from touching the fluids from a checkenpox blister, or if someone with chickenpox coughs or sneezes near you. The vaccine usually prevents the chickenpox disease completely or makes the illness very mild. Even those with mild illness may be contagious.

When someone becomes infected, the pox usually appear 10 to 21 days later. People become contagious 1 to 2 days before breaking out with pox. They remain contagious while uncrusted blisters are present.

Most cases of chickenpox occur in children younger than 10. The disease is usually mild, although serious complications sometimes occur. Adults and older children usually get sicker than younger children do.

Children whose mothers have had chickenpox or have received the chickenpox vaccine are not very likely to catch it before they are 1 year old. If they do catch chickenpox, they often have mild cases. This is because antibodies from their mothers' blood help protect them. Children under 1 year old whose mothers have not had chickenpox or the vaccine can get severe chickenpox.

Severe chickenpox symptoms are more common in children whose immune system does not work well. This may be caused by an illness or medicines such as chemotherapy and steroids.

Symptoms

Most children with chickenpox act sick, with symptoms such as a fever, headache, tummy ache, or loss of appetite for a day or two before breaking out in the classic pox rash. These symptoms last 2 to 4 days after breaking out.

The average child develops 250 to 500 small, itchy, fluid-filled blisters over red spots on the skin.

  • The blisters often appear first on the face, trunk, or scalp and spread from there. Appearance of the small blisters on the scalp usually confirms the diagnosis.
  • After a day or two, the blisters become cloudy and then scab. Meanwhile, new crops of blisters spring up in groups. The pox often appear in the mouth, in the vagina, and on the eyelids.
  • Children with skin problems such as eczema may get more than 1,500 pox.

Most pox will not leave scars unless they become infected with bacteria from scratching.

Some children who have had the vaccine will still develop a mild case of chickenpox. They usually recover much more quickly and have only a few pox (less than 30). These cases are often harder to diagnose. However, these children can still spread chieckenpox to others.

Signs and tests

Chickenpox is usually diagnosed from the classic rash and the child's medical history. Blood tests, and tests of the pox blisters themselves, can confirm the diagnosis if there is any question.

Treatment

In most cases, it is enough to keep children comfortable while their own bodies fight the illness. Oatmeal baths in lukewarm water provide a crusty, comforting coating on the skin. An oral antihistamine can help to ease the itching, as can topical lotions. Trim the fingernails short to reduce secondary infections and scarring.

Safe antiviral medicines have been developed. To work well, they usually must be started within the first 24 hours of the rash.

  • For most otherwise healthy children without severe symptoms, antiviral medications are usually not used. Adults and teens, who are at risk for more severe symptoms, may benefit if the case is seen early in its course.
  • For those with skin conditions (such as eczema or recent sunburn), lung conditions (such as asthma), or those who have recently taken steroids, the antiviral medicines may be very important. The same is also true for adolescents and children who must take aspirin on an ongoing basis.
  • Some doctors also give antiviral medicines to people in the same household who subsequently come down with chickenpox. Because of their increased exposure, they would normally experience a more severe case of chickenpox.

DO NOT GIVE ASPIRIN to someone who may have chickenpox. Use of aspirin has been associated with a serious condition called Reyes Syndrome. Ibuprofen has been associated with more severe secondary infections. Acetaminophen may be used.

Until all chickenpox sores have crusted over or dried out, avoid playing with other children, going back to school, or returning to work.

Expectations (prognosis)

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

Once you have had chickenpox, the virus usually remains dormant or asleep in your body for your lifetime. About 1 in 10 adults will experience shingles when the virus re-emerges during a period of stress.

Complications

  • Women who get chickenpox during pregnancy are at risk for congenital infection of the fetus.
  • Newborns are at risk for severe infection, if they are exposed and their mothers are not immune.
  • A secondary infection of the blisters may occur.
  • Encephalitis is a serious, but rare complication.
  • Reye's syndrome, pneumonia, myocarditis, and transient arthritis are other possible complications of chickenpox.
  • Cerebellar ataxia may appear during the recovery phase or later. This is characterized by a very unsteady walk.

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

Because chickenpox is airborne and very contagious before the rash even appears, it is difficult to avoid. It is possible to catch chickenpox from someone on a different aisle in the supermarket, who does not even know they have chickenpox!

A chickenpox vaccine is part of the routine immunization schedule.

  • Children receive two doses of the traditional chickenpox vaccine. The first should be given when the child is 12 - 15 months old. Children should receive the second dose when they are 4 - 6 years old.
  • People ages 13 and older who have not received the vaccine and have not had chickenpox should get two doses, 4 - 8 weeks apart.

Almost no one will develop moderate or severe chickenpox if they have received the chickenpox vaccine. The small number of children who do develop chickenpox after they have received the vaccine have only a mild case.

The chickenpox vaccine does not require a booster later in life. However, a similar but different vaccine given later in life may reduce the incidence of herpes zoster (shingles).

Talk to your doctor if you think your child might be at high risk for complications and might have been exposed. Immediate preventive measures may be important. Giving the vaccine early after exposure may still reduce the severity of the disease.

References

Myers MG, Seward JF, LaRussa PS. Varicella-zoster virus. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbook of Pediatrics. 18th ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 250.

American Academy of Pediatrics Committee on Infectious Diseases. Recommended immunization schedules for children and adolescents--United States, 2008. Pediatrics. 2008;121:219-220.

This article uses information by permission from Alan Greene, M.D., © Greene Ink, Inc.


Review Date: 9/13/2009
Reviewed By: Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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