Varicella-Zoster Virus

Subtitle Infection Control in Healthcare Personnel: Epidemiology and Control of Selected Infections Transmitted Among Healthcare Personnel and Patients (2024)

At a glance

Varicella-Zoster Virus from the Infection Control in Healthcare Personnel: Epidemiology and Control of Selected Infections Transmitted Among Healthcare Personnel and Patients (2024) guideline.

Recommendations

Recommendations
  1. For asymptomatic healthcare personnel with evidence of immunity to varicella (https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5604a1.htm#box)1 who have an exposure to varicella (chickenpox) or disseminated or localized herpes zoster (shingles):
  • Postexposure prophylaxis is not necessary.
  • Work restrictions are not necessary.
  • Implement daily monitoring for signs and symptoms of varicella from the 8th day after the first exposure through the 21st day after the last exposure.
  1. For asymptomatic healthcare personnel without evidence of immunity to varicella who have an exposure to varicella (chickenpox) or disseminated or localized herpes zoster (shingles):
  • Administer postexposure prophylaxis in accordance with CDC and ACIP recommendations (https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6228a4.htm; https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5604a1.htm). 2,3
  • Exclude from work from the 8th day after the first exposure through the 21st day after the last exposure.
    • Work restrictions are not necessary for healthcare personnel who received one dose of the varicella vaccine prior to exposure if they receive the second dose of vaccine within 5 days after exposure.
      • Implement daily monitoring for signs and symptoms of varicella from the 8th day after the first exposure through the 21st day after the last exposure.
    • If varicella-zoster immune globulin is administered as postexposure prophylaxis, exclude from work from the 8th day after the first exposure through the 28th day after the last exposure.
  1. For healthcare personnel with varicella (chickenpox), exclude from work until all lesions have dried and crusted; or, for those who only have non-vesicular lesions that do not crust, exclude from work until no new lesions appear within a 24-hour period.
  1. For healthcare personnel with disseminated herpes zoster (shingles) or for immunocompromised healthcare personnel with localized herpes zoster until disseminated disease has been ruled out, exclude from work until all lesions have dried and crusted.
  1. For immunocompetent healthcare personnel who have localized herpes zoster (shingles), including vaccine-strain herpes zoster, and for immunocompromised healthcare personnel who have localized herpes zoster and have had disseminated disease ruled out:
  • Cover all lesions and, when feasible, exclude from direct care of patients at high risk for severe varicella (e.g., in protective environments) until all lesions are dried and crusted.
  • If lesions cannot be covered (e.g., on the hands or face), exclude from work until all lesions have dried and crusted.
For recommendations about healthcare personnel who are pregnant or intending to become pregnant, please see the Pregnant HCP section.

Background

Varicella-zoster virus (VZV) is a DNA virus that is a member of the herpesvirus group. Primary infection with VZV causes varicella (chickenpox), and reactivation of latent infection causes herpes zoster (shingles). Healthcare-associated transmission of VZV is well recognized,45 although reports of transmission in healthcare settings have become less common since the introduction of the varicella vaccine.6789 Sources for healthcare-associated transmission include patients, healthcare personnel (HCP), and visitors with either varicella or herpes zoster.10

Prevention of transmission of VZV in healthcare settings involves (a) ensuring HCP have evidence of immunity to varicella11; (b) using infection prevention and control practices as recommended by CDC (https://www.cdc.gov/infection-control/hcp/isolation-precautions/appendix-a-type-duration.html#V)12; (c) administering postexposure prophylaxis (PEP) to susceptible HCP exposed to varicella or herpes zoster; and (d) excluding potentially infectious HCP from work.13 CDC recommends that susceptible HCP should not enter the room of a patient with varicella, disseminated herpes zoster, or localized herpes zoster if immune caregivers are available.14

The criteria for evidence of immunity to varicella (https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5604a1.htm#box)15 and recommendations for varicella vaccination of HCP (https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5604a1.htm; https://www.cdc.gov/mmwr/preview/mmwrhtml/rr6007a1.htm)310 are maintained by CDC and the Advisory Committee on Immunization Practices (ACIP).

Occupational Exposures

VZV can be spread from person to person by direct contact, inhalation of small particles from vesicular fluid of skin lesions of acute varicella or herpes zoster that remain suspended in the air, and possibly through infectious respiratory secretions from patients with varicella that also may be suspended in the air.16

Varicella and Disseminated Herpes Zoster

Unprotected (e.g., not wearing recommended personal protective equipment) contact with patients with varicella or disseminated herpes zoster, their secretions, or air containing infectious particles is typically considered an exposure to VZV. Exposures in healthcare settings may include unprotected entry into a source patient’s room (or shared air space) or touching vesicular fluid from skin lesions without personal protective equipment. Experts differ regarding the duration of exposure to an infectious patient (e.g., being in the same room) that is needed for transmission. Sources suggest time frames from 5 minutes to up to 1 hour.3 Using a shorter time frame (e.g., 5 minutes) for considering an unprotected HCP to be exposed, might better ensure that HCP at risk for developing disease are identified. Brief, unprotected entry into a source patient’s room (or shared air space) without touching the patient or surfaces is generally not considered an exposure.

Localized Herpes Zoster

VZV can also spread from a person with active localized herpes zoster to cause varicella in a susceptible person (i.e., who has never had varicella or has not received varicella vaccine).17 The lesions of localized (or disseminated) herpes zoster are infectious until they dry and crust over; covering the lesions reduces the risk of transmission to others.

For HCP with localized herpes zoster, covering lesions serves the two-fold purpose of reducing the risk of transmission to others, as well as protecting the compromised skin from contamination and potential secondary infection. Data on the efficacy of one type of covering (e.g., sterile bandage, gauze, clothing, etc.) versus another for preventing virus transmission are limited.1819 Some facilities have policies regarding what types of dressings may be used to cover lesions for HCP with localized herpes zoster to report to work.

Clinical Features

Varicella, or chickenpox, is the acute, infectious febrile rash illness that results from primary infection with VZV.2021 After primary infection, VZV establishes latency in the sensory nerve ganglia. Herpes zoster, or shingles, is the reactivation of latent VZV and occurs in approximately one-third of those infected over their lifetime.

The incubation period for varicella is on average 14 to 16 days after exposure to a varicella or a herpes zoster rash, with a range of 10 to 21 days.22 A person with varicella is considered contagious from 1-2 days before rash onset until all lesions have crusted.22 A person with active herpes zoster is contagious when the rash is vesicular, and no longer infectious to others once the rash has crusted over.17 Herpes zoster is less contagious than varicella, and the risk of a person with herpes zoster spreading the virus is low if the rash is covered.1417

A varicella-like rash can occur at the injection site after receipt of varicella vaccine and is generally self-limited. Transmission of vaccine virus to others is rare.2023 More information about the transmission of vaccine virus can be accessed from the CDC website (https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5604a1.htm).3

Varicella (chickenpox)

Varicella is highly contagious, with secondary infection occurring in 61-100% of susceptible household contacts. Varicella is characterized by a pruritic, maculopapular vesicular rash that evolves into noninfectious dried crusts over a 4-7 day period.21 A mild prodrome of fever and malaise may occur 1 to 2 days before rash onset, particularly in adults.22 Acute varicella is generally mild and self-limited, but it may be associated with complications.20 Immunocompromised and pregnant adults without evidence of immunity to varicella are at increased risk for severe varicella (https://www.cdc.gov/chickenpox/hcp/clinical-guidance/index.html).24 Examples of immunocompromised HCP at high risk for severe varicella include those with leukemia or lymphoma, cellular immune-deficiencies, and on medications that suppress the immune system such as high dose steroids or chemotherapeutic agents.16 Immunocompromised persons are at risk for developing visceral dissemination, pneumonia, hepatitis, encephalitis, and disseminated intravascular coagulopathy.24 In addition, they can present with increased numbers of skin lesions that may be atypical (i.e., hemorrhagic), that can continue to develop, and that can have longer duration than immunocompetent hosts with varicella. Pregnant persons without evidence of immunity to varicella are at risk for complications of varicella, such as VZV pneumonia, with increased frequency and severity in the 3rd trimester. If an individual develops varicella in the first or early second trimester of pregnancy, the baby is at risk for congenital varicella syndrome; if the individual develops a varicella rash from 5 days before to 2 days after delivery, the baby is at risk for neonatal varicella.24

Breakthrough varicella is infection occurring in a vaccinated person more than 42 days post-vaccination.22 Breakthrough disease is generally milder than disease in unvaccinated persons, often with fewer than 50 skin lesions, mostly maculopapular with few vesicles, compared with 300 or more skin lesions, mostly vesicular in unvaccinated persons.22 Given its modified clinical presentation, breakthrough varicella can be challenging for practitioners to recognize. Persons with breakthrough disease are still contagious to others, though they usually are less so than unvaccinated persons with varicella.2225

Herpes zoster (shingles)

Herpes zoster usually presents as a vesicular rash with pain and itching in a localized dermatomal distribution.26 The rash may also be disseminated – defined as the appearance of lesions outside the primary or adjacent dermatomes – mainly in immunocompromised persons.26 Postherpetic neuralgia (PHN), or pain in the area of the rash that persists after the lesions have resolved, is a complication of herpes zoster.2026

Testing and Diagnosis

The clinical diagnosis of varicella has become increasingly challenging as a growing proportion of cases occur in vaccinated persons in whom disease is mild and modified, and HCP encounter patients with varicella less frequently.327 Given these factors, laboratory testing to confirm the diagnosis in affected HCP has become increasingly important. Polymerase chain reaction (PCR) is the laboratory testing method of choice to confirm varicella. Ideal samples for testing are vesicular fluid or crusts from skin lesions.2829 VZV may also be isolated in tissue culture, although this method is less sensitive and requires several days to obtain results.2021

The signs and symptoms of herpes zoster are usually distinctive enough to make an accurate clinical diagnosis once the rash has appeared.30 However, clinical diagnosis of herpes zoster might not be possible in the absence of a rash, and laboratory testing can confirm VZV infection when the rash may be similar in appearance to other diseases, such as herpes simplex virus.303132

Additional information regarding VZV testing is available on the CDC website (https://www.cdc.gov/chickenpox/php/laboratories/index.html)33 and (https://www.cdc.gov/shingles/hcp/clinical-overview/index.html#cdc_clinical_overview_test_dia-testing).30

Postexposure Prophylaxis (PEP)

ACIP recommends that exposed HCP without evidence of immunity to varicella receive postexposure vaccination as soon as possible (https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5604a1.htm)3 Vaccination within 3 to 5 days of exposure may modify the disease if infection occurs.3 Vaccination 6 or more days after exposure is still indicated because it induces protection against subsequent exposures.3

For HCP without evidence of immunity to varicella who have a contraindication to varicella vaccination and are at increased risk for severe disease (e.g., pregnant, immunocompromised), varicella-zoster immune globulin is recommended to be administered as soon as possible (within 10 days) after exposure to VZV.23 Administration of immune globulin can prolong the incubation period to 28 days after exposure.2 Detailed information regarding dosage and administration of PEP is available on the CDC website (https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6228a4.htm; https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5604a1.htm).2,3,33

Considerations for When HCP with Localized Herpes Zoster Continue to Work

For immunocompetent HCP with localized herpes zoster that can be completely covered, risk for transmission to patients or other HCP is low, and these HCP typically remain at work. Restricting these HCP from providing direct care to those at high risk for severe varicella (https://www.cdc.gov/chickenpox/hcp/clinical-guidance/index.html)24 might provide an added layer of protection for these patients, but is not readily implemented when these patients are not easily identified (e.g., evidence of immunity to varicella is unknown). Hence, restricting these HCP from caring for patients at high risk for severe varicella may be reasonably applied in selected situations (e.g., restricted from caring for patients placed in a protective environment, such as a hematopoietic stem cell transplant unit or neonatal intensive care unit).

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Content Source:
National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)
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  2. Centers for Disease Control and Prevention. Updated recommendations for use of VariZIG--United States, 2013. Updated July 19, 2013. Accessed 2024, February 14. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6228a4.htm
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  28. Dollard S, Chen M, Lindstrom S, Marin M, Rota P. Diagnostic and Immunologic Testing for Varicella in the Era of High-Impact Varicella Vaccination: An Evolving Problem The Journal of infectious diseases. 2022;226(Supplement_4):S450-S455. doi:10.1093/infdis/jiac363
  29. Roush S, Beall B, McGee L, et al. Manual for the Surveillance of Vaccine-Preventable Diseases. Updated February 7, 2024. Accessed February 14, 2024. https://www.cdc.gov/surv-manual/php/table-of-contents/chapter-22-laboratory-support.html
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