Scarlet Fever

Scarlet fever is an acute respiratory infection caused by group A β-hemolytic Streptococcus, characterized by fever, pharyngitis, diffuse bright-red rash with subsequent desquamation; a minority develop allergic cardiorenal/joint complications. Incubation 2-12 days (usually 2-5), abrupt onset with fever, pharyngitis, and rash.

Common Symptoms

Macule; desquamation; lymphadenopathy; sore throat; stupor; low fever; roseoliform rash; pruritus

Causes and Pathogenesis

Bacteria invade and adhere to the pharynx causing inflammation, red swollen tonsils with serofibrinous exudate/ulcers; lymphatic spread causes peritonsillar abscess, sinusitis, otitis media, mastoiditis, cervical lymphadenitis, cellulitis; severe cases develop septicemia and metastatic abscesses. Erythrogenic toxin enters the blood causing fever, headache, anorexia; it dilates skin vessels, causes edema/epithelial proliferation/leukocyte infiltration (perifollicular), producing the typical rash, then epidermal desquamation; petechial mucosal bleeding; hepatosplenic/lymph node congestion and fatty change; myocardial cloudy swelling; renal interstitial inflammation; toxic CNS changes. Post-streptococcal complications (cardiorenal/joint) occur at weeks 2-3 due to immune complex deposition. Group A streptococci are cocci in chains 0.6-1.0 µm, Gram-positive, encapsulated, non-motile, catalase-negative, β-hemolytic on blood agar; >90 M serotypes. Virulence relates to capsule, M protein, erythrogenic toxin, and enzymes; lipoteichoic acid/M protein mediate adhesion; hyaluronate capsule/M protein resist phagocytosis. Erythrogenic toxin has 5 serotypes without cross-immunity; streptolysins/streptokinase contribute. It survives weeks in sputum/pus, killed by 56°C/30 min or disinfectants.

Treatment

Drug therapy, supportive therapy

Preventive Measures

No active vaccine; focus on spread control. Isolate children until two negative throat cultures. Weak/immunocompromised close contacts receive TMP-SMX or penicillin prophylaxis; carriers need 10 days of penicillin. (1) Manage sources: isolate patients/carriers 6-7 days; penicillin for 2 days converts ~95% of throat cultures; quarantine child institutions for 1 week after last case; extend isolation for persistent positives. (2) Cut transmission: avoid public places during epidemics; ventilate rooms; isolate suspected patients/carriers. (3) Protect susceptibles: benzathine penicillin 0.6-0.9 MU (children) / 1.2 MU (adults) protects 30 days; or sulfadiazine 1 g/day or sulfadoxine 0.5 g/week.

Department to Visit

It is recommended to visit the Infectious Diseases department; an appointment can be booked on this platform before the visit.

Warm reminder: The above information is for health science reference only and cannot replace professional medical diagnosis. If you have related symptoms, please seek medical attention at a regular hospital promptly.