A highly contagious disease, usually encountered in childhood, caused by hemolytic streptococus. It is spread through the air or through contaminated food, and was virtually untreatable before the development of antibiotics, although penicillin and gamma globulin have made it much less common in the twentieth century.
Scarlet fever's onset is sudden (typically two to seven days after exposure), beginning with a sore throat, shivering, and a headache. It develops on the second day into a rash behind the ears, which spreads to the arms and legs. Thomas Sydenham, a physician of the late seventeenth century, describes its symptoms thus: "The skin is marked with small, red spots, more frequent, more diffuse, and more red than in measles. These last two or three days. They then disappear, leaving the skin covered with brawny squamulae [scales], as if powdered with meal." Scarlet fever leaves the glands swollen and often sensitive; in some cases, the squamulae on parts of the patient's skin peel off.
The greatest threats arise from complications. Sinus infections, abcesses of the ear, and mastoiditis are common. In a few cases, scarlet fever leads to arthritis, rheumatic fever, or kidney failure.