Diphtheria (Greek διφθερα (diphthera)—“pair of leather scrolls")'s an upper respiratory tract illness characterized by sore throat, low fever, and an adherent membrane (a pseudomembrane) on the tonsils, pharynx, and/or nasal cavity. A milder form of diphtheria can be restricted to the skin. It's caused by Corynebacterium diphtheriae, an aerobic Gram-positive bacterium. Diphtheria causes the progressive deterioration of myelin sheaths in the central… (More on Diphtheria)