Scarlet Fever
Aetiology and epidemiology
Scarlet fever or scarlatina is an exotoxin-mediated disease arising from Group A beta-haemolytic streptococci (GABHS). Over one hundred different M protein types have been identified.
The organism is mainly spread by aerosol or droplet spread; although it can also be found in contaminated foods.
The incubation period for scarlet fever is usually 2-5 days. The infectivity period is about 5 days from when the patient is given antibiotics.
Clinical assessment
Scarlet fever usually begins with a sore throat, headache, fever, tender cervical lymphadenopathy and malaise. In children, abdominal pain may also occur. This is then followed by a confluent erythematous rash (A) with a sandpaper-like quality.
Other associated features include:
- Strawberry tongue (B)
- Pastias lines (C) in the flexural folds
- Circumoral pallor
- Pharyngitis
- Desquamation of hands, feet and groin
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| Fig 1: Rash | Fig 2: Strawberry tongue | Fig 3: Pastias lines |
Clinical presentations
A broad spectrum of clinical presentations associated with scarlet fever are listed in Table 1.
| Impetigo and pyoderma | Erysipelas | Vaginitis |
| Bacteraemia | Pneumonia | Pericarditis |
| Septic arthritis | Necrotising fasciitis | Toxic shock syndrome |
Investigations
A variety of diagnostic tests for scarlet fever are available, see Table 2. There are, however, limitations associated with each investigation.
| Test | Limitation |
|---|---|
| Streptococcal antibody test | Streptococcal antibody tests are not indicated during acute illness but may confirm previous infection |
| Throat swab culture test | Throat swab culture tests can be performed, but a good quality specimen is required. This is the gold standard test for scarlet fever but results can take 24-48 hours |
| Rapid diagnostic tests | Rapid antigen testing is not routinely recommended for sore throats in the UK. The specificities are generally high but the sensitivities vary and depend on the quality of the throat swab specimen [6] |
Management
Scarlet fever is a notifiable disease and notification is required based on clinical suspicion.
Antibiotic treatment is indicated (penicillin V or erythromycin or cephalosporin) for 10 days.
Health Protection Agency guidance advises that children diagnosed with scarlet fever should be excluded from school for 5 days following the commencement of antibiotics.
The majority of texts advise 24 hours off school post-commencement of antibiotics for group A streptococcal pharyngotonsillitis alone.
Complications
Problems can arise from a range of complications associated with scarlet fever.
| Sinusitis |
| Mastoiditis |
| Peritonsillar abscess |
| Pneumonia |
| Meningitis |
| Osteomyelitis |
| Septic arthritis |
| Cerebral abscess |
| Septicaemia |
| Myocarditis |
| Toxic shock-like syndrome |
| Glomerulonephritis |
| Acute rheumatic fever |
Note that the risks of post-streptococcal glomerulonephritis and acute rheumatic fever in the UK are low.