| Image = Diphtheria bull neck.5325 lores.jpg
| Caption = Diphtheria causes a characteristic swollen neck, sometimes referred to as ?bull neck?.
| Width = 150
| DiseasesDB = 3122
| ICD10 =
| ICD9 =
| ICDO =
| OMIM =
| MedlinePlus = 001608
| eMedicineSubj = emerg
| eMedicineTopic = 138
| eMedicine_mult =
| MeshID = D004165
}}Diphtheria (Greek ??????? (diphthera) — ?pair of leather scrolls?), is 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 is caused by Corynebacterium diphtheriae, a facultatively anaerobic Gram-positive bacterium.Office of Laboratory Security, Public Health Agency of Canada Corynebacterium diphtheriae Material Safety Data Sheet. January 2000.Diphtheria is a highly contagious disease spread by direc