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Chickenpox

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Chickenpox is a viral infection in which a person develops extremely itchy blisters all over the body. It used to be one of the classic childhood diseases. However, it has become much less common since the introduction of the chickenpox vaccine.

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Causes
Chickenpox is caused by the varicella-zoster virus, a member of the herpesvirus family. The same virus also causes herpes zoster (shingles) in adults.

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

A person with chickenpox becomes contagious 1 to 2 days before their blisters appear. They remain contagious until all the blisters have crusted over.

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.

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 because of an illness or medicines such as chemotherapy and steroids.

Symptoms
Most children with chickenpox have the following symptoms before the rash appears: The chickenpox rash occurs about 10 to 21 days after coming into contact with someone who had the disease. The average child develops 250 to 500 small, itchy, fluid-filled blisters over red spots on the skin. 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 (fewer than 30). These cases are often harder to diagnose. However, these children can still spread chickenpox to others.

Exams and Tests
Your health care provider can usually diagnose chickenpox by looking at the rash and asking questions about the person's medical history. Small blisters on the scalp usually confirm the diagnosis.

Laboratory tests can help confirm the diagnosis, if needed.

Treatment
Treatment involves keeping the person as comfortable as possible. Here are things to try: Medications that fight the chickenpox virus are available but not given to everyone. To work well, the medicine usually must be started within the first 24 hours of the rash. Do NOT give aspirin or ibuprofen 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 (Tylenol) may be used.

A child with chickenpox should not return to school or play with other children until all chickenpox sores have crusted over or dried out. Adults should follow this same rule when considering when to return to work or be around others.

Outlook (Prognosis)
Usually, a person recovers without complications.

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

Possible Complications
Rarely, serious infections such as encephalitis have occurred. Other complications may include: Cerebellar ataxia may appear during the recovery phase or later. This involves a very unsteady walk.

Women who get chickenpox during pregnancy can pass the infection to the developing baby. Newborns are at risk for severe infection.

When to Contact a Medical Professional
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.

A vaccine to prevent chickenpox is part of a child's routine immunization schedule. For information, see: Chickenpox vaccine

The vaccine usually prevents the chickenpox disease completely or makes the illness very mild.

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.

Alternative Names
Varicella; Chicken pox

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.

Update Date: 8/22/2013
Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.
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