Varicella Zoster Virus

Aka: Varicella Zoster Virus, Chickenpox, Chicken Pox, VZV

1. Epidemiology
   1. Peak onset ages 5 to 9 years old
   2. Outbreak time: January to May
   3. Incidence: 3.7 Million cases/year in U.S. 1980-1990
   4. Varicella Immunity
      1. Adults (U.S): 95% immune
      2. Adults (U.S.) without known VZV history: 75% immune
2. Etiology
   1. Herpes Varicella Zoster Virus
   2. Human Herpes Virus (Herpesviridae)
3. Transmission
   1. Direct contact
   2. Respiratory droplet
   3. Transplacental
4. Symptoms
   1. Viral Prodrome
      1. Fever
      2. Anorexia
      3. Malaise
      4. Headache
      5. Myalgia
   2. Pruritic rash
      1. See signs for description
5. Signs
   1. Generalized Lymphadenopathy
   2. Rash
      1. Crops of small, Red Papules
      2. Develop into "Dew Drop on a rose petal" Appearance
         1. Oval, "teardrop" Vesicles
         2. Erythematous base
      3. Spread from trunk to face
         1. Minimal limb involvement
         2. May involve oral or vaginal mucosa
      4. Images
         1. 
6. Differential Diagnosis
   1. Herpes Simplex Virus
   2. Herpes ZosterVirus (Shingles)
   3. Impetigo
   4. Coxsackie virus
   5. Papular Urticaria
   6. Scabies
   7. Dermatitis Herpetiformis
   8. Drug rash
7. Labs
   1. Complete Blood Count (CBC)
      1. Slight Leukocytosis
   2. Vesicular fluid exam (Tzanck Smear)
      1. Multinucleated giant cells
      2. Epithelial cells with Eosinophilic inclusion bodies
      3. Virus
   3. IgG Antibody to VZV (ELISA)
      1. Immunity testing indicated in pregnancy
8. Management: General
   1. Reduction of Pruritus
      1. Calamine Lotion
      2. Oatmeal Bath (Aveeno)
      3. Atarax at bedtime
   2. Prevention of Superinfection
      1. Apply Bacitracin to denuded lesions until scab forms
9. Management: Virus Suppression
   1. Normal host: Acyclovir
      1. Dose: 20 mg/kg/dose up to 800 mg/dose 5x/day or q4h
      2. Efficacy
         1. Shortens time of viral shedding
         2. Most effective if started within 24 hours of rash
            1. Faster cessation of new lesions
            2. Fever duration reduced
            3. More rapid healing
      3. Indications
         1. Consider especially in large household
      4. Adverse effects
         1. Avoid if dehydration present
         2. Not associated with short-term viral resistance
      5. References
         1. Balfour (2001) Pediatr Infect Dis J 20:219-26
   2. Immunocompromised or pregnancy exposure <20 weeks
      1. VZIG within 96 hours of exposure
         1. Dose: 5 vials Varicella Zoster Immunoglobulin
      2. Acyclovir
         1. Initiate as soon as possible with onset of rash
         2. Indicated within 10 days of rash onset
         3. Dose: 500 mg/m2/day IV divided q8 hours for 7 days
10. Prevention
    1. Varicella Vaccine (Varivax)
11. Course
    1. Incubation period: 11-21 days
    2. Infectious
       1. Start: 1-3 days before rash
       2. End: Final lesion crusted
12. Complications
    1. Lung involvement (14-30% of adults)
       1. PneumoniaIncidence 1 case per 400 adult cases
    2. Encephalitis
    3. Secondary bacterial infection (superinfection) common
       1. Cellulitis
       2. Abscess
       3. Erysipelas
       4. Invasive Group A Beta-hemolytic Streptococcus
          1. Incidence: 5.2 cases per 100,000 VZV cases
          2. Increasing Incidence
          3. Suspect if fever persists >3-4 days after exanthem
       5. Septic Arthritis
       6. Osteomyelitis
       7. Staphylococcal pyomyositis
       8. Disseminated disease in immunocompromised
    4. Reye's Syndrome
       1. Avoid concurrent Aspirin use
    5. Nephritis
    6. Varicella mortality (1987-1992)
       1. United States: 80-100 per year (mostly children)
       2. Death occurs once every 4 days in United States
       3. Most deaths occur under age 20 years old
       4. Death often in otherwise healthy children
13. Complications: Congenital Syndrome (Pregnancy related)
    1. General
       1. Non-immune Mother exposed to Varicella Zoster Virus
       2. Congenital syndrome risk prior to 20 weeks gestation
       3. Not associated with Pregnancy loss
       4. Not associated with Preterm Labor
    2. Infant Findings
       1. Skin lesions
       2. Short limbs and digits
       3. Ocular abnormalities
       4. Muscular atrophy
       5. Intrauterine Growth Retardation
14. References
    1. Doctor (1995) Pediatrics 96:428-33