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Scarlet Fever

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.

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.

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.

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)

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.

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

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]