Chickenpox (Varicella)


Chickenpox is a highly contagious disease caused by the varicella-zoster virus (VZV). It can cause an itchy, blister-like rash. The rash first appears on the chest, back, and face, and then spreads over the entire body. Chickenpox can be serious, especially in babies, adolescents, adults, pregnant women, and people with a weakened immune system. The best way to prevent chickenpox is to get the chickenpox vaccine.

In the prevaccine era, varicella was endemic in the United States, and virtually all persons acquired varicella by adulthood. As a result, the number of cases occurring annually was about 4 million. The majority of cases (approximately 90%) occurred among children younger than age 15 years. The incidence of varicella has decreased significantly since U.S. vaccination began in 1995. Overall, varicella incidence declined an average of 97% from prevaccine years.

Only chickenpox outbreaks are reportable in Iowa. An outbreak is defined as five or more cases that are related in place and epidemiologically linked.  Outbreaks are reportable by Iowa Administrative Code 641 Chapter 1.

If you are a childcare provider or school staff and think there may be an outbreak of chickenpox in your facility, please fill out this survey here or call the Center for Acute Disease Epidemiology at (800)362-2736. 


  • Generalized, itchy, rash
  • Blisters containing fluid
    • The blisters commonly occur in successive crops of skin and oral mucous membranes
    • Blisters are more abundant on covered than exposed parts of the body
  • Tiredness
  • Fever
  • Headache
  • Loss of appetite


The varicella zoster virus replicates in the upper respiratory tract.  Chickenpox is easily spread from person to person by droplet or airborne spread of respiratory tract secretions, or contact with the fluid of the blisters. 

A person with chickenpox is contagious beginning one to two days before rash onset and until all blisters have crusted. Vaccinated people who get chickenpox may develop lesions that do not crust. These people are considered contagious until no new lesions have appeared for 24 hours.

Chickenpox occurs approximately 10 to 21 days after exposure.


Varicella vaccine should be administered to all adolescents and adults 13 years of age and older who do not have evidence of varicella immunity. Two doses of varicella vaccine is more than 90% effective at preventing disease. Vaccination is recommended for all children starting at 12 to 15 months of age with a second dose at four to six years of age.

Individuals with varicella should stay home until all of their lesions have crusted. During outbreaks, it may be recommended for exposed susceptible individuals who refuse vaccination or have contraindications to the varicella vaccine, stay home from school or childcare. In these situations, exclusion is required for the duration of the period of communicability (from the eighth until the 21st day post-exposure).

Childcare and Schools

Call CADE to report chickenpox outbreaks at (800) 362-2736 or fill out this survey

Unvaccinated children with no history of varicella disease should be instructed to be vaccinated immediately. If vaccination is contraindicated or refused, the child may be excluded from school up to 21 days after the last case is identified. A notification letter should be sent home with children informing parents and caregivers of the outbreak. The notification letter should alert the person to the possibility of exposure to varicella, describe the disease, recommend vaccination if the person is not already considered immune, and recommend exclusion if disease develops. Children with uncomplicated chickenpox who have been excluded from school or childcare may return when the rash has crusted, or in immunized people without crusts, when lesions have faded or no new lesions have appeared in the last 24 hours. The scope of those exposed will be based on whether there are multiple classrooms that do or do not intermingle. 

Pregnant women, infants, and unvaccinated people with a weakened immune system that have been exposed to chickenpox may be at risk for severe disease. These individuals should be evaluated promptly for post exposure prophylaxis or treatment.


Calamine lotion and a cool bath with added baking soda, uncooked oatmeal, or colloidal oatmeal may help relieve some of the itching. Try to minimize scratching to prevent the virus from spreading to others and potential bacterial infection from occurring. Keeping fingernails trimmed short may help prevent skin infections caused by scratching blisters.

Appropriate antiviral drugs appear useful in preventing or modifying varicella in exposed individuals if given for seven days starting seven to 10 days after exposure. Always consult your health care provider if you have questions about your health or before starting any treatment.

Additional Resources

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