Chicken Pox

Organism
Varicella-zoster virus (hepesvirus) – only 1 recognized strain, humans are the only source of infection

Transmission

  • Person-to-person by direct contact with varicella/zoster and respiratory secretions (droplets)
  • Most cases between 5-9 years old
  • Risk of more severe disease in extremes of age and immunocompromised

Incubation

  • 10 – 21 days after contact
  • Most contagious 2 days before rash develops until all lesions crusted over (longer in immunocompromised)
  • Prodrome: 1-2 days before rash with malaise and mild fever

Differential diagnosis

Vesicular rash

  • Coxsackie virus (hand, foot and mouth disease)
  • Rickettsial pox
  • Molluocerm contagorm
  • Eczema herpeticum
  • Herpes zoster with dissemination

Rash
Successive crops of macules, papules and vesicules – crops appear every 3 days
“A dew drop on a rose petal”
3 phases:

  1. Maculopapular, progressing from head to toe
  2. Vesicular
  3. Crusting and healing (non-infectious)

Tests
Serology – only to determine presence of immunity
PCR – rapid diagnostic test for use in high risk individuals

Complications (esp in neonates and immunocompromised)

  • Secondary bacterial infection
  • Pneumonia
  • Encephalitis
  • Meningitis
  • Necrotizing enterocolitis

Treatment

  • Neonates: if mother has a rash 5 days antepartum or 2 days postpartum
  • Immunocompromised
    • <72hr VZIG
    • >72hr IV Acyclovir
  • Healthy children – Tylenol, cool baths, Calamine lotion and Benadryl for itch

Prevention
Varivax: live attenuated virus (97% seroconversion rate)

  • Healthy children at 1 years old
  • <13 yo without immunity – 1 dose
  • ≥13 yo without immunity – 2 doses 1-2months apart
  • Contraindicated in pregnancy and immunosuppressed

History

  • Characterize rash (onset, position, progression, appearance, change over time, pruritis)
  • Prodromal symptoms (fever, malaise, HEENT, resp, abdo, GU, MSK)
  • Exposure to anyone with rash… when?
  • Complications?
  • Past medical history, Social, family history, Immunizations, medications, Allergy/Atopy

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