Scarlet fever
Last revised in July 2023
Scarlet fever is a notifiable infectious disease caused by toxin-producing strains of the group A streptococcus bacterium (Streptococcus pyogenes).
Diagnosis
Management
Prescribing information
Background information
Scarlet fever: Summary
- Scarlet fever (or 'scarlatina') is an infectious disease caused by toxin-producing strains of the bacterium Streptococcus pyogenes, also known as group A streptococcus (GAS).
- The incubation period is usually 2–3 days. People can be infectious for 2–3 weeks after the onset of symptoms, unless they are treated.
- It is highly contagious and is transmitted when a person's mouth, throat, or nose comes into contact with infected saliva or mucus by aerosol transmission or by direct contact.
- An outbreak is defined as 'a credible report of two or more probable or confirmed scarlet fever cases attending the same school or nursery or other childcare setting, notified within 10 days of each other (two maximum incubation periods), with an epidemiological link between cases, for example they are in the same class or year group'.
- People who are at increased risk of invasive Group A streptococcal infection (iGAS) and complications include people:
- At extremes of the age range, such as the very young and old, or postpartum women.
- Who are immunocompromised, immunosuppressed, or with other comorbidities.
- With concurrent chickenpox or influenza.
- Who inject drugs or are alcohol dependent.
- Scarlet fever can occur at any age but is most common in children between 2–8 years of age. There has been an upsurge in notified cases since 2013/14.
- Complications may include:
- Suppurative complications due to local spread, such as otitis media, peritonsillar abscess, and acute sinusitis.
- Non-suppurative (immune-mediated) complications, such as acute rheumatic fever and acute post-streptococcal glomerulonephritis.
- Invasive GAS infection, such as pneumonia, meningitis, streptococcal toxic shock syndrome, or necrotizing fasciitis.
- In most cases, the clinical features of infection resolve over about 1 week.
- A diagnosis of scarlet fever should be suspected if there is:
- Initial sore throat, fever, headache, fatigue, nausea, and vomiting.
- A pinpoint, sandpaper-like blanching rash that develops on the trunk 12–48 hours after initial symptoms, before spreading to the rest of the body and flexures.
- Possible strawberry tongue, cervical lymphadenopathy, circumoral pallor.
- Throat swabs and blood tests are not routinely indicated for the diagnosis of scarlet fever.
- Management of suspected or confirmed scarlet fever should include:
- Arranging urgent hospital admission if a person has severe symptoms or a suspected serious complication (or is at risk of serious complications).
- Prescribing appropriate oral antibiotics promptly, regardless of the severity of illness, such as phenoxymethylpenicillin for 10 days first-line.
- Notifying the local health protection team promptly.
- Advising the person or family/carers about appropriate self-care measures, and strategies to reduce the risk of cross-infection.
- Arranging follow up if symptoms worsen or have not improved after 7 days.
- Considering seeking local health protection team advice if a person is a high-risk contact.
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