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

Etiology and Pathophysiology

• Erythrogenic toxin (streptococcal pyrogenic exotoxin) production is necessary for scarlet fever to develop clinically.
• Multiple streptococcal superantigens (SpeA, SpeC, and SSA) are implicated, with GAS strains often carrying a repertoire of >10 superantigens encoded on prophages that can transfer between strains.
• The characteristic rash reflects a delayed, host-acquired hypersensitivity that occurs primarily in individuals with prior exposure to Streptococcus pyogenes.
• Antitoxin antibodies can reduce susceptibility to the rash (historically the basis of the Dick test) but do not protect against underlying GAS infection.
• The primary site of streptococcal infection is usually within the tonsils, but scarlet fever may also occur with infection of the 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., barracks, child care, schools)
• Skin lesions due to trauma, surgery, or skin disorders, heart ailments, diabetes, and cancer are other risk factors. Injection drug users have shown a higher risk of invasive GAS infection owing to their immunocompromised status

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 12 to 24 hours of antibiotic therapy.

Commonly Associated Conditions

Pharyngitis, impetigo, rheumatic fever, glomerulonephritis