Scarlet Fever

BASICS

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 (erythematous, blanchable 1 to 2 mm papules; “sand paper”) usually appears within 24 to 48 hours after symptom onset.
Rash first appears in the groin, trunk, and axillae accompanied by strawberry tongue and circumoral pallor and then rapidly spreads outward all over the body, sparing palms and soles.
Rash clears at the end of the 1st week and is followed by several weeks of desquamation.
Rash is not dangerous but is a marker for GAS infection with suppurative and nonsuppurative complications.
System(s) affected: head, eyes, ears, nose, throat, skin/exocrine
Synonym(s): scarlatina

In developed countries, 15% of school-aged 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 aged >12 years because of high rates (>80%) of lifelong protective antibodies to erythrogenic toxins

Erythrogenic toxin production is necessary for scarlet fever to develop clinically.
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/early 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, saliva, and nasal secretions
Foodborne outbreaks have been reported but are rare.
Asymptomatic contacts do not require cultures/prophylaxis.
Symptomatic contacts of a child with documented GAS infection who have recent or current clinical evidence of a GAS infection should undergo appropriate laboratory tests and should be treated if test results are positive.
Children should not return to school/daycare until they are afebrile and have received 24 hours of antibiotic therapy.

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