Chickenpox

Last updated: November 7, 2022

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Chickenpox (i.e., varicella) is an infection caused by the varicella zoster virus (VZV). The condition predominantly affects children. Transmission occurs via inhalation of airborne droplets and direct contact with respiratory secretions or skin lesion fluids. Chickenpox manifests with an intensely pruritic rash characterized by sequential clusters of papules, vesicles, and pustules in various stages of development; the rash may be preceded by a prodrome of constitutional symptoms. A clinical diagnosis is made based on the appearance of the rash; confirmatory testing may be obtained for atypical rashes or severe infection. In immunocompetent individuals, chickenpox is self-limiting and managed symptomatically. Antiviral therapy is reserved for patients with severe infection or at high risk for complications (e.g., bacterial superinfection, invasive infections). Following resolution, the virus remains latent in the sensory nerve root ganglia; it can reactivate (see “Shingles”) during episodes of stress or immunosuppression. Prevention includes routine vaccination and, when indicated, postexposure prophylaxis.

  • Primarily occurs in children
  • Before vaccines were widely introduced, ∼ 90% of all children had been infected by the age of 15.

References:[1]

Epidemiological data refers to the US, unless otherwise specified.

Risk factors for severe VZV infection [3][4][5]

Individuals with any of the following factors are at risk of severe primary infection if they have no evidence of VZV immunity:

  • Incubation period: ∼ 2 weeks [3]
  • Prodrome phase (rare in children) [7]
  • Exanthem phase: characterized by approx. 250–500 severely pruritic lesions in varying stages of development ; [3][7]
    • Lesion stages: papules→ superficial vesicles filled with clear fluid on an erythematous base (“dewdrop on rose petal” appearance) umbilicated and crusted pustules → scabs fall off after 1–3 weeks, (often leaving a depressed base)
    • Skin involvement [3][7][8]
      • Lesions first manifest centrally (i.e., face, scalp, and trunk) and spread to the extremities.
      • The rash is ultimately distributed across the body, with the highest concentration of lesions in the centeral areas.
      • The oral and urogenital mucous membranes are affected.
      • Palms and soles are typically spared.
    • Features of severe varicella infection may develop, e.g.: [3]
  • Latent phase: Following resolution of active skin infection, VZV remains latent in the sensory root ganglia; it can later reactivate (see "Shingles”). [7] [3]

Severe varicella infection is characterized by the prolonged eruption of vesicles, which are sometimes hemorrhagic, high fever > 1 week, and dissemination of VZV to the brain (encephalitis), liver (hepatitis), and/or lungs (pneumonia). [3]

Breakthrough varicella infection [3][9]

  • Definition: a wild-type VZV infection that occurs in individuals who have received ≥ 1 dose of the chickenpox vaccine ≥ 42 days prior to symptom onset [3][9][10]
  • Infectivity: infectious to close contacts [9]
  • Clinical features: generally mild compared to typical chickenpox infection [3]
    • Manifests ≥ 42 days following any dose of chickenpox immunization [9][10]
    • Shorter duration of illness and lower likelihood of fever
    • Typically < 50 skin lesions with few or no vesicles (predominantly maculopapular lesions)
  • Diagnosis: PCR test confirms a wild-type strain of VZV; see “Diagnostics of chickenpox.” [11][12]
  • Treatment: Usually supportive; follow varicella infection prevention measures to reduce spread.

Vaccine-associated chickenpox rash [3][9][13]

General principles

  • Typically diagnosed clinically based on characteristic clinical features
  • Confirmatory diagnostic studies are usually only considered in the following cases: [2][15]
    • Suspected VZV infection in patients with no rash or uncharacteristic rash
    • Vaccinated patients with suspected varicella
    • Patients with immunocompromised contacts
  • Additional studies may be required for patients with severe infections.

Confirmatory studies [15][16]

Chickenpox is usually diagnosed clinically. Obtain laboratory testing in case of atypical rash or severe infections. [2]

Additional studies

Consider in severe varicella zoster infection, depending on clinical features.

Visceral dissemination is more common in patients with HIV; consider HIV testing in patients with severe infection. [23]

Chickenpox may be confused with other conditions that involve widespread vesicles and/or crusting lesions, e.g.: [3][7]

The differential diagnoses listed here are not exhaustive.

Approach [2]

Most otherwise healthy children < 13 years of age with chickenpox can be treated with symptomatic treatment alone, but advise caregivers to return in the event of prolonged or worsening symptoms and/or signs of secondary bacterial skin infection. [2]

Supportive treatment [2]

  • Treat fever and pain with acetaminophen. [2]
  • Pruritus ; [28]
    • General advice for caregivers
      • Apply cool compresses.
      • Take lukewarm oatmeal baths.
      • Trim fingernails or wear mitts to prevent scratching.
    • Medications

Avoid use of aspirin and other salicylates (e.g., bismuth-subsalicylate) in children with chickenpox because of the risk of Reye syndrome. [3]

Avoid topical antihistamines and topical corticosteroids in patients with chickenpox because of the risk of systemic absorption when applied to large areas of skin. [29]

Antiviral therapy for VZV infection (high-risk patients only)

Patients with nonsevere infections and no risk factors for severe VZV infection do not require antiviral therapy and can be managed with supportive treatment only. [2]

Neonates, immunocompromised patients, and patients with severe infection should not receive oral acyclovir because of poor oral bioavailability. [3]

Adults have higher rates of complications from varicella compared to children. [2]

Skin [3]

Central nervous system [3][31]

Lungs [3]

Fetus (chickenpox during pregnancy) [3]

We list the most important complications. The selection is not exhaustive.

  • In healthy children, chickenpox infection generally has a benign course and heals without any consequences.
  • Residual scarring may occur because of excessive scratching or bacterial superinfection.
  • Immunosuppressed individuals are at a greater risk of the disease taking a generalized or even fatal course.

References:[2]

Approach

Most US states mandate reporting cases of chickenpox to local and/or state health departments. [32]

Evidence of VZV immunity [3][8][9]

Any of the following constitutes evidence of immunity to chickenpox: [9][33]

Chickenpox immunization [34][35]

Recommend the varicella vaccine to all nonimmune children and adults who do not have contraindications to live vaccination. [34][35]

Postexposure prophylaxis for chickenpox [4][9]

General principles

Determining postexposure prophylaxis

Recommended management [3][9][39]
Evidence of VZV immunity No evidence of VZV immunity
Immunocompetent
Immunocompromised

Active immunization

Prophylaxis is not recommended for healthy individuals who are either too young for vaccination or who were exposed to VZV > 5 days prior to evaluation. [3]

Passive immunization

Controlling varicella transmission in healthcare settings [41]

Varicella in pregnancy [6][9]

Overview

Diagnostics

Treatment

Prevention [6][9]

Pregnant women should not receive the varicella vaccine. Nonimmune women should be vaccinated after delivery. [9]

Varicella in adults [1]

Overview

Management

Varicella in patients with HIV [23]

Overview

Diagnostics

Treatment

  • Antiviral treatment is recommended. [23]
  • Discuss route of antiviral treatment with infectious diseases. [23]
    • Uncomplicated infection is usually treated with oral antivirals
    • Severe or complicated infection is usually treated with IV antivirals
  • See also “Treatment of chickenpox.”

Prevention

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