Varicella (Chickenpox)

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Introduction

  • Varicella Zoster virus is Human Herpes Virus 3
  • Transmission is by direct contact with the lesions and by the respiratory route
  • Initial replication occurs in the nasopharynx and conjunctivae
  • After the primary infection, the virus remains dormant in nervous tissue
    • Reactivation later in life is typically manifested as Herpes zoster

Clinical features

  • Incubation period is 10 - 21 days
  • Vesicular eruptions consist of delicate "teardrop" vesicles on an erythematous base
  • The eruption starts with faint macules that develop rapidly into vesicles within 24 hours
  • Successive fresh crops of vesicles appear for a few days, mainly on the trunk, face, and oral mucosa
  • New lesions usually stop appearing by the fifth day; the majority is crusted by the sixth day
    • Most disappear in less than 20 days without a scar, except larger and secondarily infected lesions
  • Low grade fever
  • Malaise
  • Headaches

The severity of the disease is age-dependent

  • Adults have more severe disease and a greater risk of visceral disease

Differential diagnoses

  • Variola minor
  • Disseminated zoster in immunosuppressed patients
  • Widespread papular urticaria
  • Coxsackie and ECHO viruses eruption

Complications

  • Secondary bacterial infection
  • Pneumonia
  • Cerebellar ataxia and encephalitis
  • Reye's syndrome

Investigations

  • Tzanck smear
  • Direct fluorescent antibody (DFA) staining
  • Polymerase Chain Reaction (PCR)

Treatment goals

  • Relieve itching and treat secondary bacterial infection
  • Reduce severity and scarring

Drug treatment

Aciclovir

Adult: 10 mg/kg intravenously three times daily for 7 days in immunocompromised patients

Child: see Herpes zoster

Antihistamine for pruritus

Co-trimoxazole or erythromycin for secondary infection

Notable adverse drug reactions, contraindications and caution

Aciclovir

  • Ensure adequate hydration
  • Caution in pregnancy and breastfeeding
  • May cause nausea, vomiting, dizziness, fatigue pruritus and photosensitivity

Prevention

  • Isolate patients from non-immune persons