An acute infectious disease caused by the varicella-zoster virus (VZV), a member of the human herpes virus family

Aetiology

• Caused by the varicella virus, specifically HHV3
• The virus is airborne and spreads through direct contact with the rash or by breathing in particles from an infected person's sneezes or coughs

Clinical features

• Rash:
  • Starts as raised red, itchy spots, primarily on the face or chest, before spreading to the rest of the body
  • Progresses into small, fluid-filled blisters over a span of a few days
  • Eventually crusts over and heals, typically leaving no scars unless the blisters have been scratched and infected
  • Peak infectivity is 1-2 days before the rash appears, until 5 days after the rash first appeared
• Other accompanying symptoms may include mild fever, fatigue, loss of appetite, and general discomfort

Investigations

• Usually clinical diagnosis
• Lab testing is typically reserved for severe cases, immunocompromised patients, or when the diagnosis is uncertain

Management

• Primarily conservative - self-limiting condition
• NICE guidelines recommend school exclusion during the most infectious period, that 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 are given oral aciclovir on days 7-14 after exposure for post-exposure prophylaxis