Erythrogenic toxins cause the rash of scarlet fever. The erythema-producing toxin was discovered by Dick and Dick in 1924. Group A streptococci are normal inhabitants of the nasopharynx. Scarlet fever usually is associated with pharyngitis but, in rare cases, follows streptococcal infections at other sites. The incubation period for Scarlet Fever ranges from 12 hours to 7 days.
Patients are contagious during the acute illness and during the subclinical phase.
A beta-hemolytic streptococci were major causes of mortality and morbidity. Now, however, because of antibiotics and improved socioeconomic conditions, there has been a dramatic decrease in the incidence and complications of such infections. The incubation period of streptococcal pharyngitis is usually 2-4 days. The rash appears 12-24 hours after the onset of the illness, first on the trunk and then extending rapidly over the entire body to finally involve the extremities. The rash can, at times, spread cephalocaudally.