GPAtlas🧭 When to suspect
Suspect scarlet fever in any child – or, less commonly, an adult – presenting with the classic triad:
• fever;
• severe sore throat (streptococcal tonsillitis);
• a characteristic fine, sandpaper-like rash.
Scarlet fever is caused by toxin-producing strains of Streptococcus pyogenes (group A streptococcus, GAS) – the same organism responsible for strep throat and impetigo – in people susceptible to the erythrogenic exotoxin.
Scarlet fever is predominantly a disease of early childhood:
• Around 90% of cases occur in children under 10, most commonly between the ages of 2 and 8 years (peak age 4).
• Most people over 10 have developed immunity to the toxin.
• England currently sees roughly 15,000–30,000 cases a year, with notifications rising markedly since 2014.
• Scarlet fever is a statutory notifiable disease.
• The diagnosis is clinical: treatment should be started on clinical suspicion rather than waiting for swab confirmation.
| Phase | Typical features |
|---|---|
| Incubation (1–7 days; usually 2–5) | • Asymptomatic • The person may already be infectious |
| Prodrome (first 12–48 h) | • Abrupt fever, sore throat with tonsillitis, headache, malaise, and often nausea or vomiting • Cough and coryza are usually absent |
| Rash phase (12–48 h after onset) | • Fine, blanching, sandpaper rash starting on the neck, chest and abdomen and spreading to the limbs (sparing palms and soles) • Flushed cheeks with circumoral pallor • Strawberry tongue • Pastia's lines in the skin folds • The rash spares the face |
| Convalescence (after ~1 week) | Desquamation – peeling of the skin, classically of the fingertips, toes and groin – as the rash fades. |
Raise suspicion particularly during the winter and spring peak and where there is a known local outbreak or close contact with a confirmed case of scarlet fever or streptococcal sore throat. Scarlatina (a milder form) may present with the rash and few other symptoms.
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