Overview

Chickenpox is an infection caused by the varicella-zoster virus. It causes an itchy rash with small, fluid-filled blisters. Chickenpox is highly contagious to people who haven't had the disease or been vaccinated against it. Today, a vaccine is available that protects children against chickenpox. Routine vaccination is recommended by the Centers for Disease Control and Prevention (CDC).

The chickenpox vaccine is a safe, effective way to prevent chickenpox and its possible complications.

Symptoms

The itchy blister rash caused by chickenpox infection appears 10 to 21 days after exposure to the virus and usually lasts about five to 10 days. Other signs and symptoms, which may appear one to two days before the rash, include:

  • Fever
  • Loss of appetite
  • Headache
  • Tiredness and a general feeling of being unwell (malaise)

Once the chickenpox rash appears, it goes through three phases:

  • Raised pink or red bumps (papules), which break out over several days
  • Small fluid-filled blisters (vesicles), which form in about one day and then break and leak
  • Crusts and scabs, which cover the broken blisters and take several more days to heal

New bumps continue to appear for several days, so you may have all three stages of the rash — bumps, blisters and scabbed lesions — at the same time. You can spread the virus to other people for up to 48 hours before the rash appears, and the virus remains contagious until all broken blisters have crusted over.

The disease is generally mild in healthy children. In severe cases, the rash can cover the entire body, and lesions may form in the throat, eyes, and mucous membranes of the urethra, anus and vagina.

When to see a doctor

If you think you or your child might have chickenpox, consult your doctor. He or she usually can diagnose chickenpox by examining the rash and considering other symptoms. Your doctor can also prescribe medications to lessen the severity of chickenpox and treat complications, if necessary. To avoid infecting others in the waiting room, call ahead for an appointment and mention that you think you or your child may have chickenpox.

Also, let your doctor know if:

  • The rash spreads to one or both eyes.
  • The rash gets very red, warm or tender. This could indicate a secondary bacterial skin infection.
  • The rash is accompanied by dizziness, disorientation, rapid heartbeat, shortness of breath, tremors, loss of muscle coordination, worsening cough, vomiting, stiff neck or a fever higher than 102 F (38.9 C).
  • Anyone in the household has a problem with his or her immune system or is younger than 6 months.

Causes

Chickenpox infection is caused by a virus. It can spread through direct contact with the rash. It can also spread when a person with the chickenpox coughs or sneezes and you inhale the air droplets.

Risk factors

Your risk of becoming infected with the varicella-zoster virus that causes chickenpox is higher if you haven't already had chickenpox or if you haven't had the chickenpox vaccine. It's especially important for people who work in child care or school settings to be vaccinated.

Most people who have had chickenpox or have been vaccinated against chickenpox are immune to chickenpox. If you've been vaccinated and still get chickenpox, symptoms are often milder, with fewer blisters and mild or no fever. A few people can get chickenpox more than once, but this is rare.

Complications

Chickenpox is normally a mild disease. But it can be serious and can lead to complications including:

  • Bacterial infections of the skin, soft tissues, bones, joints or bloodstream (sepsis)
  • Dehydration
  • Pneumonia
  • Inflammation of the brain (encephalitis)
  • Toxic shock syndrome
  • Reye's syndrome in children and teenagers who take aspirin during chickenpox
  • Death

Who's at risk?

People who are at higher risk of chickenpox complications include:

  • Newborns and infants whose mothers never had chickenpox or the vaccine
  • Adolescents and adults
  • Pregnant women who haven't had chickenpox
  • People who smoke
  • People whose immune systems are weakened by medication, such as chemotherapy, or by a disease, such as cancer or HIV
  • People who are taking steroid medications for another disease or condition, such as asthma

Chickenpox and pregnancy

Low birth weight and limb abnormalities are more common among babies born to women who are infected with chickenpox early in their pregnancy. When a mother is infected with chickenpox in the week before birth or within a couple of days after giving birth, her baby has a higher risk of developing a serious, life-threatening infection.

If you're pregnant and not immune to chickenpox, talk to your doctor about the risks to you and your unborn child.

Chickenpox and shingles

If you've had chickenpox, you're at risk of a complication called shingles. The varicella-zoster virus remains in your nerve cells after the skin infection has healed. Many years later, the virus can reactivate and resurface as shingles — a painful cluster of short-lived blisters. The virus is more likely to reappear in older adults and people who have weakened immune systems.

The pain of shingles can persist long after the blisters disappear. This is called postherpetic neuralgia and can be severe.

Two shingles vaccines (Zostavax and Shingrix) are available for adults who have had chickenpox. Shingrix is approved and recommended for people age 50 and older, including those who've previously received Zostavax. Zostavax isn't recommended until age 60. Shingrix is preferred over Zostavax.

Prevention

The chickenpox (varicella) vaccine is the best way to prevent chickenpox. Experts from the Centers for Disease Control and Prevention (CDC) estimate that the vaccine provides complete protection from the virus for nearly 98 percent of people who receive both of the recommended doses. When the vaccine doesn't provide complete protection, it significantly lessens the severity of chickenpox.

The chickenpox vaccine (Varivax) is recommended for:

  • Young children. In the United States, children receive two doses of the varicella vaccine — the first between ages 12 and 15 months and the second between ages 4 and 6 years — as part of the routine childhood vaccination schedule.

    The vaccine can be combined with the measles, mumps and rubella vaccine, but for some children between the ages of 12 and 23 months, the combination may increase the risk of fever and seizure from the vaccine. Discuss the pros and cons of combining the vaccines with your child's doctor.

  • Unvaccinated older children. Children ages 7 to 12 years who haven't been vaccinated should receive two catch-up doses of the varicella vaccine, given at least three months apart. Children age 13 or older who haven't been vaccinated should also receive two catch-up doses of the vaccine, given at least four weeks apart.
  • Unvaccinated adults who've never had chickenpox and are at high risk of exposure. This includes health care workers, teachers, child care employees, international travelers, military personnel, adults who live with young children and all women of childbearing age.

    Adults who've never had chickenpox or been vaccinated usually receive two doses of the vaccine, four to eight weeks apart. If you don't remember whether you've had chickenpox or the vaccine, a blood test can determine your immunity.

The chickenpox vaccine isn't approved for:

  • Pregnant women
  • People who have weakened immune systems, such as those who are infected with HIV, or people who are taking immune-suppressing medications
  • People who are allergic to gelatin or the antibiotic neomycin

Talk to your doctor if you're unsure about your need for the vaccine. If you're planning on becoming pregnant, consult with your doctor to make sure you're up to date on your vaccinations before conceiving a child.

Is it safe and effective?

Parents typically wonder whether vaccines are safe. Since the chickenpox vaccine became available, studies have consistently found it safe and effective. Side effects are generally mild and include redness, soreness, swelling and, rarely, small bumps at the site of the shot.

Feb. 27, 2019
References
  1. Chickenpox (varicella). Centers for Disease Control and Prevention. https://www.cdc.gov/chickenpox/about/index.html. Accessed Jan. 14, 2019.
  2. Centers for Disease Control and Prevention. Varicella (chickenpox). In: CDC Yellowbook 2018: Health Information for International Travel. New York, N.Y.: Oxford University Press; 2018. http://global.oup.com/. Accessed Jan. 14, 2019.
  3. Papadakis MA, et al., eds. Viral and rickettsial infections. In: Current Medical Diagnosis & Treatment 2019. 58th ed. New York, N.Y.: McGraw-Hill Education; 2019. https://accessmedicine.mhmedical.com. Accessed Jan. 14, 2019.
  4. Types of chickenpox vaccine. Centers for Disease Control and Prevention. https://www.cdc.gov/vaccines/vpd/varicella/public/index.html. Accessed Jan. 14, 2019.
  5. Longo DL, et al., eds. Varicella-zoster virus infections. In: Harrison's Principles of Internal Medicine. 20th ed. New York, N.Y.: The McGraw-Hill Companies; 2018. https://accessmedicine.mhmedical.com. Accessed Jan. 14, 2019.
  6. Chickenpox (varicella). Merck Manual Professional Version. https://www.merckmanuals.com/professional/infectious-diseases/herpesviruses/chickenpox. Accessed Jan. 14, 2019.
  7. Stone K, et al. BET 2: NSAIs and chickenpox. Emergency Medicine Journal: EMJ. 2018;35:66.
  8. AskMayoExpert. Herpes zoster (shingles). Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2018.
  9. Tosh PK (expert opinion). Mayo Clinic, Rochester, Minn. Feb. 1, 2019.

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