Scarlet Fever

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Scarlet fever is an infectious disease caused by Group A Streptococcus (Streptococcus pyogenes) bacteria. It is characterised by a distinctive red rash, sore throat, and fever.

Aetiology

Scarlet fever is caused by Group A Streptococcus bacteria, which produce an erythrogenic toxin that leads to the characteristic rash. The bacteria are typically spread through respiratory droplets from an infected person.

Pathophysiology

The pathophysiology of scarlet fever involves:

• Infection with Group A Streptococcus bacteria.
• The bacteria produce erythrogenic toxins, which spread through the bloodstream.
• The toxins cause dilation of blood vessels and a characteristic red rash.
• Inflammation of the throat and other systemic symptoms are also caused by the bacteria and their toxins.

Risk Factors

• Children aged 5-15 years
• Close contact with an infected individual (e.g., in schools or daycare centres)
• Recent strep throat or skin infection
• Weakened immune system

Signs and Symptoms

The signs and symptoms of scarlet fever include:

• Red rash that feels like sandpaper, typically starting on the chest and spreading to other areas of the body
• Sore throat
• High fever
• Strawberry tongue (red and bumpy appearance)
• Red lines (Pastia's lines) in the creases of the skin folds, such as the armpits and groin
• Flushed face with a pale area around the mouth
• Headache
• Nausea and vomiting
• Swollen glands in the neck

Investigations

Specific investigations to diagnose scarlet fever include:

• Throat swab: To detect Group A Streptococcus bacteria.
• Rapid antigen detection test (RADT): To quickly identify Group A Streptococcus antigens from a throat swab.
• Blood tests: Full blood count (FBC) to check for elevated white blood cell count and other indicators of infection.

Management

Primary Care Management

• Antibiotics: Penicillin or amoxicillin is the first-line treatment. For those allergic to penicillin, a cephalosporin, clindamycin, or azithromycin can be used.
• Supportive care: Ensuring adequate hydration, rest, and management of symptoms such as fever and throat pain with antipyretics and analgesics (e.g., paracetamol, ibuprofen).
• Infection control: Advising on measures to prevent spread, such as staying home from school or work until at least 24 hours after starting antibiotics.

Specialist Management

• Hospitalisation: Rarely needed but may be required for severe cases or complications such as rheumatic fever or glomerulonephritis.
• Management of complications: Treating severe manifestations like rheumatic fever, kidney disease, or abscesses.
• Public health measures: Reporting cases to public health authorities to monitor and prevent outbreaks.

References

1. NHS (2024) Scarlet fever. Available at: https://www.nhs.uk/conditions/scarlet-fever/ (Accessed: 24 June 2024).
2. Centers for Disease Control and Prevention (2024) Scarlet Fever: A Group A Streptococcal Infection. Available at: https://www.cdc.gov/scarletfever/index.html (Accessed: 24 June 2024).
3. Public Health England (2024) Scarlet Fever: guidance and data. Available at: https://www.gov.uk/government/collections/scarlet-fever-guidance-and-data (Accessed: 24 June 2024).
4. National Institute for Health and Care Excellence (2024) Scarlet fever. Available at: https://cks.nice.org.uk/scarlet-fever (Accessed: 24 June 2024).

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