Varicella

Background

  • Caused by varicella zoster virus causing varicella (chicken pox) and later zoster (Shingles)
  • Contagious until last lesion crusts over

Clinical Features

  • Pruritic generalized vesicular exanthem with mild systemic manifestations
  • Usually affects children <10y

Rash

  • Starts on trunk or scalp as pruritic, red macules, spreads to extremities
  • Within 24hr rash becomes vesicular (on erythematous base)
  • Palms/soles spared
  • Lesions in various stages of development

Complications

  • Can include encephalitis, otitis media, pneumonia, hepatitis, strep/staph superinfection of ruptured vesicles
  • Perinatal infection in neonates may develop serious illness

Differential Diagnosis

Pediatric Rash

Vesiculobullous rashes

Febrile

Afebrile

Varicella zoster virus

Evaluation

  • Typically made on clinical features

Management

Supportive Care

  • Tylenol, antihistamine, oatmeal baths
  • Avoid aspirin in young children due to the risk of Reye syndrome

Antivirals

  • Routine use of antiretrovirals for uncomplicated cases in immunocompetent children is not recommended [1]
  • However, evidence shows decreased days of fever and number of lesions[2]

AAP recommends antiviral treatment (within 24hrs) for patients at risk of increased illness severity:

  • Any patient older than 12 years of age
  • Patients with chronic cutaneous or pulmonary disorders
  • Patients receiving long-term salicylate therapy
  • Patients receiving short, intermittent, or aerosolized courses of corticosteroids

Other cases to consider acyclovir

  • Also consider in [3]:
  • Pregnancy[4]

Immunocompetent Adult

  • Acyclovir 800mg PO q6hrs daily x 5 days OR
  • Valacyclovir 1000mg PO q8hrs daily x 14 days OR
  • Famiciclovir 500mg PO q8hrs x 14 days

Immunocompromised Adult

At risk children <12yo child based on AAP criteria

VZIG

  • Initiate VZIG alongside acyclovir for inpatient treatment of child or adult
  • For immunocompromised child with exposure, give as post-exposure prophylaxis if[5]:
    • Within 10 days window of exposure
    • VZIG given IM as 125 IU/10 kg of body weight
      • Up to max of 625 IU
      • Minimum dose 62.5 IU for patients weighing ≤ 2.0 kg
      • Minimum dose 125 IU for weight 2.1 - 10.0 kg
  • VZIG may prolong incubation period ≥1 week
    • Must have patient closely follow up for signs and symptoms for 28 days after exposure
    • If signs or symptoms of varicella occur, antiviral therapy must be started immediately

Disposition

  • Most often discharge
  • Secondary bacterial infection most common cause of hospitalization in kids
  • Pneumonia most common cause of hospitalization in adults[6]

Vaccine

  • Introduced in 2006. Prior to introduction, incidence prior to adolescence approached 90% in US
  • Vaccine is 85% effective against all disease, 90% effective against severe disease (greater than 1000 lesions)
  • Typically given at age 5 in USA
  • Post-exposure prophylaxis:
    • Ideally given within 3-5 days of exposure in immunocompetent patients
    • If immunocompromised patient is being given VZIG, varicella vaccine should be administered ≥5 months after VariZIG administration[7]

See Also

References

  1. Arvin AM: Antiviral therapy for varicella and herpes zoster. Semin Pediatr Infect Dis 2002; 13:12.
  2. Klassen TP, et al. Acyclovir for treating varicella in otherwise healthy children and adolescents. Cochrane Database Syst Rev. 2005; (4):CD002980.
  3. Drugs for non-HIV viral infections. Treat Guidel Med Lett. 2007; 5(59):59-70.
  4. CDC Chicken pox acyclovir treatment
  5. CDC. MMWR - updated recommendations for use of VariZIG - United States, 2013. July 19, 2013 / 62(28);574-576.
  6. Reynolds MA, Watson BM, Plott-Adams KK, et al. Epidemiology of varicella hospitalizations in the United States, 1995-2005. J Infect Dis. 2008;197 Suppl 2:S120-S126. doi:10.1086/522146
  7. CDC. Prevention of varicella: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 2007;56(No. RR-4).
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