Varicella, also known as chicken pox, is a highly contagious disease caused by  varicella-zoster virus (VZV).  It is a reportable disease in Illinois.

Clinical presentation 

People with varicella classically develop a diffuse (generalized) and itchy maculopapular rash that progresses to a vesicular rash before crusting over into scabs. The rash is usually more concentrated on the face, scalp, and trunk. Infected individuals might also develop fatigue and fever, which usually appear 1–2 days before rash onset. Illness usually lasts 4–7 days.

In vaccinated persons who develop “breakthrough” varicella more than 42 days after vaccination, the disease is almost always mild with fewer than 50 skin lesions and a shorter duration of illness. The rash might also be atypical in appearance (maculopapular with few or no vesicles).

Primary infection with VZV causes varicella (chickenpox), whereas reactivation of VZV causes herpes zoster (shingles). Herpes zoster is not a reportable disease in Illinois.

Varicella complications

Varicella is generally mild in young children, but can be severe in newborns, adults, pregnant persons, and immunocompromised individuals. The most common complications from varicella are bacterial infections of the skin and soft tissues (in children) and pneumonia (in adults). Other severe complications include cerebellar ataxia, encephalitis, viral pneumonia, and hemorrhagic conditions. 

Testing/Specimen Collection

Implementation of a national varicella vaccination program has led to a sharp decline in the number of U.S. varicella cases. This has resulted in decreased familiarity among clinicians of the disease’s signs and symptoms. Additionally, clinical diagnosis can be challenging in mild or breakthrough cases with atypical rash. Consequently, laboratory confirmation of varicella is now recommended to confirm diagnosis, and this laboratory-based confirmation is increasingly necessary to understand the true burden of disease.

Laboratory tests

  • Polymerase chain reaction (PCR) is the preferred method of laboratory confirmation for varicella; it is the most sensitive and most timely method for confirming infection. 
  • Other highly specific but less sensitive methods for confirming infection are direct fluorescent antibody assay (DFA) and viral culture.
  • Paired acute and convalescent sera showing a four-fold rise in IgG antibodies have excellent specificity for varicella but have low sensitivity. A fourfold rise in IgG antibody may not occur in vaccinated persons.
  • IgM antibody testing is not recommended, because available methods lack sensitivity and specificity.

Specimen collection

Specimens for varicella lab confirmation can be collected as long as the patient has active lesions or crusts. PCR, DFA, and culture specimens can be collected by unroofing a vesicle and rubbing the base of a skin lesion with a polyester swab. These specimens can also be collected from scabs or crusted-over lesions. 

Collecting specimens from maculopapular lesions in vaccinated people is challenging but can still be useful for diagnostic testing.

Please see the CDPH Varicella Job Aid for Providers for important information about varicella, including information on testing and specimen requirements. (Lab information last updated 2019.)

Testing at the IDPH Public Health Laboratory (PHL)

  • The IDPH PHL does not routinely test for varicella zoster virus. Commercial labs providing VZV PCR testing can be found on the Varicella Job Aid for Providers . (Lab information last updated 2019.) 
  • The IDPH PHL can coordinate genotype testing of varicella specimens to distinguish rashes due to wild-type VZV from rashes caused by vaccine type (Oka/Merck)-strain VZV.
    • Cases where VZV typing might be useful include those with rash onset 7 to 42 days after vaccination, herpes zoster in a vaccinated person, and suspected secondary vaccine-strain VZV transmission.
    • CDPH must approve all requests for testing at the IDPH PHL. To request testing, please contact the VPD reporting line (312-743-9000).
    • Specimens submitted to the IDPH lab should be collected and processed according to the CDC specimen collection and shipping instructions, located here: Test Order | Submitting Specimens to CDC | Infectious Diseases Laboratories | CDC


Treatment for varicella is usually limited to symptom relief. However, antiviral medications may be recommended for people with chickenpox who are more likely to develop serious disease. Acyclovir, an antiviral medication, is licensed for treatment of chickenpox. For more information, see the CDC’s guidance on Managing People at High Risk for Severe Varicella. Other antiviral medications that may also work against chickenpox include valacyclovir and famciclovir.

Post-exposure Prophylaxis

Varicella vaccine

Following exposure to varicella or herpes zoster, immunocompetent individuals 12 months and older without evidence of immunity and without contraindications for varicella vaccine should be offered varicella vaccine as soon as possible and ideally within 5 days of exposure. 

  • Vaccination within 3 to 5 days of exposure might prevent infection or modify the disease if infection occurred. 
  • Vaccination >5 days post-exposure should still be given, because it induces protection against subsequent exposures if the current exposure did not cause infection.

VariZIG (Varicella Ig) 

People without evidence of immunity to varicella who are at high risk for severe varicella and complications, who have been exposed to varicella or herpes zoster, and for whom varicella vaccine is contraindicated, should receive VariZIG within 10 days of exposure. Groups recommended by CDC to receive VariZIG include the following: 

  • Immunocompromised people without evidence of immunity. 
  • Newborn infants whose mothers have signs and symptoms of varicella around the time of delivery (i.e., 5 days before to 2 days after). 
  • Hospitalized premature infants born at ≥28 weeks of gestation whose mothers do not have evidence of immunity to varicella. 
  • Hospitalized premature infants born at <28 weeks of gestation or who weigh ≤1,000g at birth, regardless of their mothers' evidence of immunity to varicella. 
  • Pregnant women without evidence of immunity.

Clinicians should consult with their pharmacy department to determine if VariZIG is in stock. If VariZIG is not in stock, clinicians will need to coordinate with pharmacy to order VariZIG directly from the manufacturer’s website (https://www.varizig.com/uspage.html). CDPH does not stock VariZIG. 

Infection Prevention and Control/Vaccination

Transmission of Varicella-Zoster Virus

VZV is spread by direct contact and inhalation of aerosols from vesicles or respiratory secretions. Nosocomial transmission of VZV is well recognized. Sources for nosocomial exposures have included patients, healthcare personnel (HCP), and visitors (including the children of patients) with either varicella (chickenpox) or herpes zoster (shingles).

A person with varicella is considered contagious beginning one to two days before rash onset until all the chickenpox lesions have crusted. Vaccinated people may develop lesions that do not crust. These people are considered contagious until no new lesions have appeared for 24 hours. It takes from 10 to 21 days after exposure to the virus for someone to develop varicella. 

Routine Vaccination

CDC recommends 2 doses of varicella (chickenpox) vaccine for children, adolescents, and adults to protect against varicella. Children should receive the first dose at age 12 through 15 months and the second dose at age 4 through 6 years old. Both a single-antigen varicella vaccine (Varivax) and a combination measles, mumps, rubella, and varicella (ProQuad) vaccine are licensed for use in the United States. Both vaccines contain live, attenuated varicella-zoster virus derived from the Oka strain. Additional information, including dosage, administration, and contraindications can be found at Varicella Vaccination Information for Healthcare Professionals.

Health care personnel without evidence of immunity to varicella should receive two doses of varicella vaccine administered 4—8 weeks apart. If >8 weeks elapse after the first dose, the second dose may be administered without restarting the schedule. Further information on vaccination of healthcare presonnel, including acceptable evidence of immunity, can be found in CDPH’s Clinical Guidelines for Management of HCP Exposed to Varicella 2022.

Management of Patients with Varicella

  • Mask patient and accompanying family members as soon as VZV infection is suspected.
  • Immediately remove patient from waiting rooms and other public areas and place them in a negative air-flow room, if available.
    • If a negative air-flow room is unavailable, place the patient in a private room with the door closed. 
  • Follow standard, airborne, and contact precautions until lesions are dry and crusted.
  • In immunocomporimised patients with varicella pneumonia, precautions should be maintained for the full duration of illness. 
  • Patients with varicella should be cared for by staff with documented evidence of immunity to varicella.

Management of Patients with Herpes Zoster (Shingles)

Infection control measures depend on whether the patient with herpes zoster is immunocompetent or immunocompromised and on whether the rash is localized or disseminated (defined as appearance of lesions outside the primary or adjacent dermatomes). In all cases, standard infection control precautions should be followed in addition to the transmission-based precautions in the table below.
               Localized HZ Disseminated HZ
Completely cover lesions and follow standard precautions until lesions are dry and crusted Airborne and contact precautions until lesions are dry and crusted
Airborne and contact precautions until disseminated infection is ruled out.

After dissemination is ruled out, completely cover lesions and follow standard precautions until lesions are dry and crusted
Airborne and contact precautions until lesions are dry and crusted.

Varicella exposures in healthcase Settings

Patients and visitors with significant exposures to VZV should be evaluated for evidence of immunity and offered postexposure prophylaxis if indicated. For additional details on identification of patients exposed to VZV and recommendations related to management of patient exposures see CDPH’s Guidelines for Prevention and Management of Varicella in Healthcare Settings

Health care personnel exposed to VZV should be evaluated for evidence of immunity and managed according to CDPH’s Clinical Guidelines for Management of HCP Exposed to Varicella 2022.

Varicella Exposures in Non-Healthcare Settings

For schools, see here for reporting and management information. For other congregate settings, including shelters, behavioral health, and correctional facilities, please contact specialpops@cityofchicago.org for guidance.

Additional Resources

Varicella Reporting

For Questions:  Contact the CDPH Disease Reporting Hotline at 312-743-9000.

Schools:  Please click here for reporting and management information.

To Report Suspect or Confirmed Cases:

Suspect or confirmed Cases must  be reported within 24 hours.  

Do not wait for laboratory confirmation.

If you have access to I-NEDSS (Illinois Notifiable Electronic Disease Surveillance System), please report via that electronic system. For all others, use the Online Case Reporting Form (preferred) OR contact the CDPH Disease Reporting Hotline at 312-743-9000.

*After hours (4:30pm – 8:30am), weekends, and holidays, call 311 (or 312-744-5000 from outside the City of Chicago) and ask for the CDPH Medical Director on call.

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