Chickenpox (Varicella)

Overview

Chickenpox is a primary infection with the varicella-zoster virus (VZV). It is highly contagious and usually self-limiting in healthy children but can be severe in adults, pregnant people, neonates, and those who are immunocompromised.

Incubation 10–21 days (≈14 typical)

Infectious period~24 h before rash → all lesions crusted

Transmission: Respiratory droplets/aerosols; direct contact with vesicle fluid

Clinical Features

Prodrome

• Fever, malaise, headache, ± upper-respiratory symptoms (more evident in older children/adults).

Rash

• Macules → papules → clear vesicles → pustules → crusts; lesions appear in crops with multiple stages visible concurrently.
• Usually starts on scalp/trunk, spreads to face and limbs; mucosal involvement can occur.
• Intensely pruritic.

Differential diagnosis

Hand-foot-mouth disease, impetigo, insect bites, disseminated zoster, eczema herpeticum, measles (if coryza/conjunctivitis/Koplik’s spots), drug eruption.

Assessment & Investigations

• Clinical diagnosis in routine cases; investigations are rarely required in immunocompetent children.
• Consider VZV PCR from vesicle fluid or serology (IgG/IgM) if atypical, severe, pregnancy, neonate, or immunocompromised.
• Assess for complications: secondary bacterial infection, pneumonia, CNS involvement, dehydration.

Management

Supportive care (most cases)

• Fluids, rest, loose clothing; maintain skin hygiene.
• Antipyretic: paracetamol as needed.
• Pruritus relief: oral antihistamines (e.g., chlorphenamine at night if appropriate), topical emollients/calamine, oatmeal baths.
• Avoid scratching; keep nails short to reduce secondary infection.
• Avoid NSAIDs in children due to possible association with severe skin/soft-tissue infection.

Antivirals (selected cases)

• Not routinely indicated in otherwise healthy children with uncomplicated disease.
• Consider oral aciclovir if started within 24 hours of rash onset in immunocompetent adolescents/adults at higher risk of complications.
• Use antivirals promptly (and consider IV therapy) for severe disease, immunocompromise, or complications—seek specialist advice.

Special groups

• Pregnancy: urgent risk assessment (immune status, exposure timing). Consider VZV serology, VZIG where indicated, and early antiviral therapy; involve obstetrics/ID.
• Neonates: exposure near delivery or maternal primary infection warrants neonatal team input ± VZIG/antiviral per local protocol.
• Immunocompromised: manage with specialist guidance; lower threshold for antivirals/IV therapy and admission.

Prevention

Vaccination

• Varicella vaccine available in the UK for specific groups (e.g., non-immune healthcare workers, close contacts of vulnerable patients) — check local policy.
• Two doses recommended; breakthrough infections tend to be milder.

Post-exposure prophylaxis (PEP)

• For eligible high-risk contacts (pregnant, neonates, immunocompromised): consider VZIG and/or antiviral prophylaxis as per UKHSA/local guidance.
• Time-critical: ideally within 96 hours of significant exposure.

Red Flags & Referral

• Persistent high fever, severe lethargy, or dehydration.
• Respiratory distress, chest pain, haemoptysis (suspect pneumonia).
• Neurological symptoms: severe headache, confusion, ataxia, seizures (suspect encephalitis/ataxia).
• Rapidly worsening skin pain, swelling, erythema, or necrosis (secondary bacterial infection).
• Any severe disease in pregnancy, neonates, or immunocompromised patients.

Infection Control & Exclusion

• Exclude from school/work and from contact with susceptible high-risk individuals until all lesions are crusted.
• Follow local occupational health policy for healthcare workers.

This content is for education and does not replace clinical judgement. Consult local guidelines and medicines information before prescribing.