What kind of condition is diphtheria?

Bad infection. Diphtheria is an upper respiratory tract illness caused by corynebacterium diphtheriae, a facultative anaerobic, gram-positive bacterium.[1][2] it is characterized by sore throat, low fever, and an adherent membrane (a pseudomembrane) on the tonsils, pharynx, and/or nasal cavity.[3] a milder form of diphtheria can be restricted to the skin.