Varicella-Zoster Virus - VZV

 

Clinical Background

Varicella-zoster virus (VZV) is the cause of chickenpox in children and herpes zoster (shingles) in adults.

Epidemiology

  • Incidence – estimated 1,000,000 new cases annually in the U.S.
  • Age
    • Varicella – children (usually 1-9 years)
    • Herpes zoster – >60 years
  • Sex – M:F, equal
  • Climate variation
    • Temperate climates – 90% of people have infection before adolescence
    • Tropical climates – more adults are susceptible than in temperate climates

Organism

  • DNA virus
  • Member of the Herpesviridae family
  • Establishes latency in sensory ganglia

Risk Factors

  • For non-immune individuals, direct contact with large-particle droplets
  • Risk factors for herpes zoster include immune deficiency, psychological stress and localized physical trauma

Clinical Presentation

  • Varicella (chickenpox)
    • Fever and generalized vesicular exanthem
      • Rash begins as macules and rapidly progresses from papules to vesicles
      • Successive crops of lesions
  • Complications
    • Secondary bacterial infections
    • Invasive infections – pneumonia, osteomyelitis
    • Central nervous system – strokes (vasculopathy), cerebellar ataxia, meningitis, transverse myelitis
  • Herpes zoster (reactivation of VZV)
    • Characterizations:
      • Skin eruption (shingles)
        • Unilateral, painful maculopapular lesions followed by vesicular eruptions with dermatomal distribution (1-3 dermatomes is usual) that does not cross the midline
      • Facial nerve (7th cranial nerve) involvement (Ramsey-Hunt syndrome)
      • Pain from inflammation of sensory nerve ganglia
      • May mimic other serious medical conditions (eg, myocardial infarction, appendicitis, acute cholecystitis, renal colic, pulmonary embolism, glaucoma)
      • Less common manifestations include pneumonitis, acute retinal necrosis, myelitis, vasculopathy, hepatitis and meningoencephalitis
      • Complications
        • Postherpetic neuralgia (PHN)
        • Secondary skin infection from Streptococcus pyogenes or Staphylococcus aureus
  • Congenital infection  – congenital VZV transmission (0.4-2% of children when mother had VZV during first 20 weeks of pregnancy) may cause severe disseminated neonatal infection with the following:
    • Pneumonia
    • Skin lesions
    • Hemorrhages
    • Death 
    • Developmental problems, including hypoplastic limbs, cataracts, chorioretinitis, microphthalmos

Treatment

  • Early treatment of zoster with antivirals accelerates resolution and may lessen post-herpetic pain

Prevention

  • Childhood vaccination preventive for VZV in most cases
  • Universal vaccination has decreased outbreaks and severity of secondary complications
  • New vaccine recently approved for adults >60 years to prevent herpes zoster
    • Vaccine shown to reduce the incidence of PHN by 66.5%
  • Passive immunization with varicella-zoster immune globulin (VZIG) can prevent severe disease in certain susceptible pediatric populations after an exposure