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What is chickenpox?

Chickenpox is a highly infectious childhood disease caused by the varicella-zoster virus (VZV), a form of the herpes virus. Before a vaccination was developed, almost every child got chickenpox, which is characterized by little blisters all over the body. Nowadays, the availability of an effective vaccine has radically reduced the number of chickenpox cases. Caused by the varicella-zoster virus (VZV), a form of the herpes virus, chickenpox can be a mild disease. However, some people suffer more serious complications.

Transmission of chickenpox occurs from person to person by direct contact or through the air. The chickenpox vaccine is very good at preventing most cases and reduces the severity in those it doesn't prevent.

Family members who have never had chickenpox have a 90 percent chance of becoming infected when another family member in the household is infected. It's important not to scratch chickenpox blisters. Complications from chickenpox can occur in infants, adults and people with weak immune systems.

Is chickenpox common?

More than 95 percent of American adults have had chickenpox and about 4,000,000 people get chickenpox every year. Since the chickenpox vaccine was introduced in 1995, less and less children are getting the disease.

Can chickenpox be prevented?

Since 1995, a chickenpox vaccine has been available for children 12 months of age and older. The vaccine has proven very effective in preventing severe chickenpox. According to the Centers for Disease Control and Prevention (CDC) about 15 to 20 percent of people who have received one dose of chickenpox vaccine do still get chickenpox, but experience a mild case. Children who received two doses of the vaccine were three times less likely to get the disease than those who only had one dose.

  • The vaccine is recommended by the CDC Advisory Committee on Immunization Practices, the American Academy of Pediatrics and the American Academy of Family Physicians.
  • A booster vaccination is recommended between 11 and 12 years of age.
  • Two doses are recommended for children over 13 who are getting the vaccine for the first time.
  • Catch-up immunization may be given as needed between the ages of 7 to 18 years.
  • Many schools now require vaccination prior to entry into preschool or public schools.

Chickenpox | Symptoms & Causes

What causes chickenpox?

Chickenpox is extremely contagious. It spreads from person to person by direct contact or through the air.

  • Chickenpox is contagious for one to two days before the appearance of the rash and until the blisters have dried and become scabs.
  • Children should stay home and away from other children until all of the blisters have scabbed over.
  • Family members who have never had chickenpox have a 90 percent chance of becoming infected when another family member in the household is infected.
  • Most individuals who have had chickenpox will be immune to the disease for the rest of their lives. However, there is a chance of developing shingles later in life, or even a secondary case of chickenpox.

What are the symptoms of chickenpox?

Symptoms are usually mild among children, but may be life-threatening to infants, adults and people with weak immune systems. While symptoms vary from child to child, the most common include:

  • fatigue and irritability one to two days before the rash begins
  • itchy rash on the trunk, face, under the armpits, on the upper arms and legs, inside the mouth, and, sometimes, in the windpipe and bronchial tubes
  • fever
  • decreased appetite
  • muscle and/or joint pain
  • cough or runny nose

Infants, adults and people with weak immune systems who get chickenpox are at risk for serious complications. They include:

  • secondary bacterial infections
  • pneumonia
  • encephalitis (inflammation of the brain)
  • cerebellar ataxia (defective muscular coordination)
  • transverse myelitis (inflammation along the spinal cord)
  • Reye syndrome (a serious condition which may affect all major systems or organs)
  • in extremely rare cases, death

Chickenpox | Diagnosis & Treatments

How does a doctor diagnosis chickenpox?

The chickenpox rash is unique, and a diagnosis can usually be made from a physical examination.

How is chickenpox treated?

For the most part, the chickenpox virus needs to run its course, but there are several things you can do to help reduce the symptoms and prevent other infections. It's very important that you don't let your child scratch the blisters, as this could lead to secondary bacterial infections. Keep your child's fingernails short to decrease the likelihood of scratching. In addition, treatments may include:

  • acetaminophen for fever (do not give aspirin)
  • antibiotics for treating bacterial infections
  • calamine lotion (to relieve itching)
  • antiviral drugs (for severe cases)
  • bed rest
  • increased fluid intake (to prevent dehydration)
  • cool baths with baking soda or Aveeno (to relieve itching)

How we care for chickenpox

The Boston Children's Hospital Informatics Program created HealthMap, an online resource and smart phone application that helps track the spread of contagious diseases, including chickenpox, in real time.

Chickenpox | Programs & Services