Introduction

Chickenpox is caused by primary infection with varicella zoster virus. Shingles is a reactivation of the dormant virus in dorsal root ganglion

Epidemiology

  • Incidence: 500.00 cases per 100,000 person-years
  • Peak incidence: 6-15 years
  • Sex ratio: 1:1
Condition Relative
incidence
Chickenpox1
Eczema herpeticum0.002
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+

Pathophysiology

Chickenpox is highly infectious
  • spread via the respiratory route
  • can be caught from someone with shingles
  • infectivity = 4 days before rash, until 5 days after the rash first appeared*
  • incubation period = 10-21 days

Clinical features

Clinical features (tend to be more severe in older children/adults)
  • fever initially
  • itchy, rash starting on head/trunk before spreading. Initially macular then papular then vesicular
  • systemic upset is usually mild

Management

Management is supportive
  • keep cool, trim nails
  • calamine lotion
  • school exclusion: NICE Clinical Knowledge Summaries state the following: Advise that the most infectious period is 1–2 days before the rash appears, but infectivity continues until all the lesions are dry and have crusted over (usually about 5 days after the onset of the rash).
  • immunocompromised patients and newborns with peripartum exposure should receive varicella zoster immunoglobulin (VZIG). If chickenpox develops then IV aciclovir should be considered

Complications

A common complication is secondary bacterial infection of the lesions
  • NSAIDs may increase this risk
  • whilst this commonly may manifest as a single infected lesion/small area of cellulitis, in a small number of patients invasive group A streptococcal soft tissue infections may occur resulting in necrotizing fasciitis

Rare complications include
  • pneumonia
  • encephalitis (cerebellar involvement may be seen)
  • disseminated haemorrhagic chickenpox
  • arthritis, nephritis and pancreatitis may very rarely be seen