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Scarlet Fever

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Overview

Scarlet fever is an infectious disease caused by specific strains of Group A Streptococcus (Streptococcus pyogenes) that produce erythrogenic (or pyrogenic) toxins. These toxins lead to an erythematous rash and can act as superantigens.

An outbreak of scarlet fever is defined as ‘a credible report of ≥2 probable or confirmed cases of scarlet fever in the same school/nursery/childcare setting notified within 10 days of each other with an epidemiological link between the cases (e.g. the same class year or group)’.

Transmission

Scarlet fever is highly contagious and spread by inhaling or ingesting respiratory droplets. Its incubation period is usually 2-3 days. People can be infectious for 2-3 weeks after the onset of symptoms unless they are treated.

Epidemiology

  • Most common in children aged 2-8 years old

Risk Factors

  • More common in people at the extremes of age (very young and old)
  • Postpartum
  • Immunocompromised/immunosuppressed
  • Comorbidities such as skin barrier breakdown, diabetes, or malignancy
  • Concurrent chickenpox
  • Concurrent influenza
  • Intravenous drug use
  • Alcohol dependency

Presentation

Scarlet fever typically presents with:

  • A non-specific prodrome lasting 12-48 hours:
  • A blanching rash – develops on the trunk after 12-48 hours after initial symptoms before spreading to the rest of the body:
    • Characteristically red, pinpoint (punctuate), generalised, and has a rough, sandpaper-like texture
    • The rash may be more accentuated in the skin folds with a deep red, linear appearance (‘Pastia’s lines’)
    • Palms and soles are usually spared
    • The skin may peel after the rash resolves, particularly around the tips of fingers and toes
  • Strawberry tongue:
    • The tongue is initially covered with a white coat followed by red papillae. The white coat disappears leaving behind a red tongue
  • Other features include:
    • Cervical lymphadenopathy
    • Flushed face and circumoral pallor
    • Pharyngitis and petechiae on the hard and soft palate (‘Forchheimer spots’)

Investigations

Overview

Treatment is started immediately based on clinical features. Throat swabs and blood tests may be considered.

Management

Overview

  • 1st-line: oral phenoxymethylpenicillin (penicillin V) for 5 days
    • If allergic: give azithromycin
  • School/nursery/work exclusion – can return 24 hours after starting antibiotics
  • Scarlet fever is a notifiable disease. Notify Public Health England.

Patient Advice

  • School/nursery/work exclusion – can return 24 hours after starting antibiotics
  • Patients should seek medical help if symptoms worsen or have not improved after 7 days.
  • Patients should seek urgent medical help if features of complications arise.

Complications

Prognosis

  • In most cases, scarlet fever is usually mild and self-limiting and most people recover in around 1 week
  • Recurrence is unlikely after infection, but patients are still susceptible to other forms of Streptococcus infection

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