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- A disease (typically in childhood) characterized by fever, pharyngitis, and rash caused by group A β-hemolytic Streptococcus pyogenes (GAS) that produces erythrogenic toxin
- Incubation period: 1 to 7 days
- Duration of illness: 4 to 10 days
- Rash usually appears on the second day of illness.
- Rash first appears on the upper chest and flexural creases and then spreads rapidly all over the body.
- Rash clears at the end of the 1st week and is followed by several weeks of desquamation.
- System(s) affected: head, eyes, ears, nose, throat, skin/exocrine
- Synonym(s): scarlatina
- In developed countries, 15% of school age children and 4–10% of adults have an episode of GAS pharyngitis each year.
- Scarlet fever is rare in infancy because of maternal antitoxin antibodies.
- Predominant age: 6 to 12 years
- Peak age: 4 to 8 years
- Predominant sex: male = female
- Rare in the United States in persons >12 years because of high rates (>80%) of lifelong protective antibodies to erythrogenic toxins
- 15–30% of cases of pharyngitis in children are due to GAS; 5–15% in adults
- <10% of children with streptococcal pharyngitis develop scarlet fever.
Etiology and Pathophysiology
- Erythrogenic toxin production is necessary to develop scarlet fever.
- Three toxin types: A, B, C
- Toxins damage capillaries (producing rash) and act as superantigens, stimulating cytokine release.
- Antibodies to toxins prevent development of rash but do not protect against underlying infection.
- Primary site of streptococcal infection is usually within the tonsils, but scarlet fever may also occur with infection of skin, surgical wounds, or uterus (puerperal scarlet fever).
- Winter/spring seasonal increase
- More common in school-aged children
- Contact with infected individual(s)
- Crowded living conditions (e.g., lower socioeconomic status, barracks, child care, schools)
- Spread by contact with airborne respiratory droplets
- Asymptomatic contacts do not require cultures/prophylaxis.
- Symptomatic contacts may be treated with or without culture.
- Children should not return to school/daycare until they have received 24 hours of antibiotic therapy.
Commonly Associated Conditions
- Rheumatic fever