Chickenpox and Shingles (VZV) - Emergency Medicine revision
Concise, ED‑focused guide to primary varicella (chickenpox) and reactivation (shingles). Emphasises recognition, infection control, high‑risk groups, when to start antivirals or request VZIG/IVIG, and where to find definitive dosing and operational procedures (GOV.UK / UKHSA).
Virology and transmission
- Causative agent: varicella zoster virus (VZV; human herpesvirus 3).
- Chickenpox = primary infection; shingles (herpes zoster) = reactivation from dorsal root or cranial nerve ganglia.
- Transmission: mainly respiratory droplets/aerosols; direct contact with vesicle fluid is infectious.
- A person with shingles can transmit VZV and cause chickenpox in a susceptible contact.
- Use GOV.UK / UKHSA guidance for public‑health procedures and notification.
Epidemiology, incubation and infectivity
- Incubation period: typically 10-21 days.
- Infectious period: about 1-2 days before rash onset until lesions have crusted (commonly ≈5 days after rash onset).
- Use infectious period for triage, isolation and workplace/school exclusion decisions (see GOV.UK guidance).
Clinical features
Chickenpox (primary VZV)
- Prodrome: fever, malaise and anorexia may precede rash.
- Rash: crops of lesions in different stages simultaneously - macules → papules → vesicles on an erythematous base (“dew‑drop on a rose petal”) → crusts.