Scarlet Fever

Description

• 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

Epidemiology

Incidence

• 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

Prevalence

• 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 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).

Risk Factors

• 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)

General Prevention

• 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.

Commonly Associated Conditions

• Pharyngitis
• Impetigo
• Rheumatic fever
• Glomerulonephritis