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Scarlet Fever

Essentials

  • Scarlet fever, also known as scarlatina, is caused by toxin-producing group A beta-haemolytic streptococci.
  • The incubation period is 3-5 days.
  • Symptoms of the disease usually include a sore throat, fever and a fine rash feeling slightly rough.
  • The disease is not usually serious but untreated it may lead to invasive, life-threatening sepsis.
  • The primary treatment is penicillin V for 10 days.

Aetiology and epidemiology

  • Erythrogenic toxin-producing group A beta-haemolytic streptococcus, i.e. Streptococcus pyogenes
  • Spreads to close contacts through droplets or contact or through contaminated food.
    • The incubation period is usually 3-5 days but varies.
    • People living with patients with scarlet fever have a clearly increased risk of severe infection.
  • The disease occurs in all age groups, mostly in children.
  • Streptococcal pharyngitis occurs commonly but scarlet fever caused by toxin-producing streptococci is much rarer.
    • Nevertheless, outbreaks do occur all the time.
  • The incidence of scarlet fever increased in the 2010s in Hong Kong and the UK, for instance.

Clinical picture

  • The symptoms are similar to A streptococcal infections in general but with a rash.
    • Fever, sore throat, headache
    • Usually associated with pharyngitis or a skin infection but may also be associated with a deep A streptococcus infection
  • The rash usually develops on the second day of disease and becomes lighter after about a week.
    • Erythematous, with small spots, often a bit rough (picture 1)
    • Usually begins on the chest
    • There is often a white triangle around the mouth, with its peak close to the nose.
    • Strawberry tongue (picture 2)
  • After the rash, the skin may scale or even peel off for a long time.

Diagnosis

  • Streptococcus pyogenes can be shown in a pharyngeal swab (or sample from another infectious focus) by culture or rapid antigen test.
  • For differential diagnosis of eruptive skin rash, see the article Exanthem (eruptive skin rash)Exanthem (Eruptive Skin Rash)

Treatment

  • Rarely requires hospital treatment.
  • Primarily phenoxymethylpenicillin for 10 days
    • All the causative streptococci are sensitive to penicillin.
    • For adults, penicillin V, 1 million IU 3 times daily
    • For children, penicillin V mixture, 66 mg/kg/day (for children over 6 years of age treated with tablets 50 000-100 000 IU/kg/day) divided into 3 doses (must not exceed the adult dose)
  • For patients with penicillin allergy
    • For adults and children over 6 years, weight > 30 kg: cephalexin 500 mg 3 times daily
    • For children 6 years, weight < 30 kg: cephalexin 25-50 mg/kg/day
  • For patients with penicillin and cephalosporin allergy, clindamycin or azithromycin can be used.
  • Infectivity ends 24 h after beginning antimicrobial treatment (the isolation period).
  • There is no vaccine available.

Criteria for referral

  • Patients with clearly impaired general condition should be referred to hospital.
  • Scarlet fever may sometimes cause an invasive septic disease leading even to shock.

    References

    • Herdman MT, Cordery R, Karo B et al. Clinical management and impact of scarlet fever in the modern era: findings from a cross-sectional study of cases in London, 2018-2019. BMJ Open 2021;11(12):e057772. [PubMed]
    • Lamagni T, Guy R, Chand M et al. Resurgence of scarlet fever in England, 2014-16: a population-based surveillance study. Lancet Infect Dis 2018;18(2):180-187. [PubMed]

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