Varicella Zoster Flashcards
Aetiology of varicella
Varicella = primary infection with VZV
- Exclusively human virus
- Incubation 2-3 weeks
- ds-DNA virus
- Transmission via direct contact or airborne spread
- establishes lifelong latency in the cranial nerves and dorsal root ganglia
Risk factors for varicella
Age 1-9
Exposure to varicella
Unimmunised status
Occupation exposure
Symptoms of varicella
Prodromal nausea, myalgia, anorexia, and headache
Sore throat
Vesicular rash
- pruritic
- dew drop on a rose petal
- first appears centrally (face, scalp, torso) before spreading to the extremities
- Macule → Papule → vesicle → crust – several stages at once
Vesicles on mucous membranes e.g. nasopharynx, conjunctiva, mouth and vuvla
Fever
Abdo pain
Investigations for varicella
Clinical diagnosis
Swab of vesicle for PCR or DFA
Tzanck smear
For assessing immune status: latex agglutination, ELISA, complement fixation
HIV serology
Management for varicella
Notify local health protection team
Advice
Aciclovir PO 800mg 4x a day for 7/7
- >14yo
- Within 24h rash onset
Analgesia e.g. Paracetamol 15mg/kg PO/PR every 4-6 hours when required
Antihistamines
- Chlorphenamine (> 1yo)
- Diphenhydramine
- Diphenhydramine topical (1-2%) 3-4x daily when required
Calamine lotion
If serious complications (pneumonia, encephalitis, dehydration, severe secondary bacterial infection of the skin) → admit to hospital
Moderate disease: oral aciclovir (>2), 20mg/kg 4x for 5 days, 800mg if >40kg
Severe disease: IV aciclovir, dose varies with age
What advice should be given for varicella
- Adequate fluid intake to avoid dehydration
- Wear smooth, cotton fabrics
- Keep nails short to minimise damage from scratching and secondary bacterial infection
- Avoid contact with those who are immunocompromised, pregnant, ages 4 weeks or less
- Children should be kept away from school or nursery until all the vesicles have crusted over
Complications of varicella
Pneumonia
Hepatitis
Encephalitis
Ocular complications
Shingles
Secondary bacterial infection e.g. impetigo, cellulitis, necrotising fasciitis
Prognosis for varicella
Typically self-limiting
Severe disease and complications are more likely to occur in children younger than 1 year of age, adolescents, adults, pregnant women, and immunocompromised people.
In up to 1/3 of infected people, VZV reactivates later