A highly contagious viral infection. Patients are contagious from 2 days before onset of the rash until all lesions have crusted. An attack of chicken pox usually confers lifelong immunity. Disease is more severe and complicated in adults.
Causes
- Varicella Zoster virus (VZV) by droplet infection
Clinical features
- Incubation period is 14 days, but shorter in immunocompromised host
- Mild fevers occur 10-20 days after exposure
- Prodromal symptoms consisting of low fever, headache, and malaise occurring 2 to 3 days before the eruption
- Eruptive phase: they appear as macules, papules, vesicles, pustules and crusts. The most characteristic lesion is a vesicle looking like a drop of water on the skin. Vesicles rupture easily and may become infected
- The rash begins on the trunk and spreads to the face and extremities
- Lesions of different stages (crops) exist together at the same time in any given body area
- Complications may include septicaemia, pneumonia, fulminating haemorrhagic varicella, and meningoencephalitis
Differential diagnosis
- Drug-induced eruption
- Scabies
- Insect bites
- Erythema multiforme, impetigo
- Other viral infections with fever and skin rash
Investigations
- Virus isolation possible but not necessary
- Diagnosis is practically clinical
Management
Symptomatic and supportive treatment
- Apply calamine lotion every 12 hours
- Cool, wet compresses to provide relief
- Chlorpheniramine: Adult 4 mg every 12 hours
Child <5 years: 1-2 mg every 12 hours for 3 days - Pain relief: paracetamol 10 mg/kg every 6 hours
In adults and children >12 years consider antivirals:
- Oral aciclovir 800 mg every 6 hours for 7 days
- Keep child at home/remove from school till healed to avoid spread
Prevention
- Isolation of infected patient
- Avoid contact between infected persons and immunosuppressed persons