Varicella Zoster

Question 1

Aetiology of varicella

Answer 1

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

Question 2

Risk factors for varicella

Answer 2

Age 1-9
Exposure to varicella
Unimmunised status
Occupation exposure

Question 3

Symptoms of varicella

Answer 3

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

Question 4

Investigations for varicella

Answer 4

Clinical diagnosis

Swab of vesicle for PCR or DFA
Tzanck smear

For assessing immune status: latex agglutination, ELISA, complement fixation
HIV serology

Question 5

Management for varicella

Answer 5

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

Question 6

What advice should be given for varicella

Answer 6

• 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

Question 7

Complications of varicella

Answer 7

Pneumonia
Hepatitis
Encephalitis
Ocular complications
Shingles
Secondary bacterial infection e.g. impetigo, cellulitis, necrotising fasciitis

Question 8

Prognosis for varicella

Answer 8

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