Because of widespread immunization, diphtheria is very rare in the United States. However, some people are not adequately vaccinated, and cases still occur. Diphtheria is caused by Corynebacterium diphtheriae, a bacterium. Diphtheria is common in many parts of the world. Diphtheria bacteria live in the mouth, nose, throat, or skin of infected persons.
Diphtheria spreads from person to person very easily.
People get diphtheria by breathing in diphtheria bacteria after an infected person has coughed or sneezed. People also get diphtheria from close contact with discharges from an infected person's mouth, nose, throat, or skin. Usually, diphtheria develops in the throat. Early symptoms are a sore throat and mild fever. A membrane that forms over the throat and tonsils can make it hard to swallow.