infectious disease

Diphtheria (pronounced "diff-THEER-ee-uh") is an infectious disease caused by a bacterium called Corynebacterium diphtheriae. It can be treated by special drugs, or by antibiotics. There is a vaccine which can prevent diphtheria. In 1942, there were 50,804 diphtheria cases in England and Wales; now there is about one case a year.[1]

The swollen 'bull neck' symptom of diphtheria

Diphtheria can cause serious problems, like:

Signs and symptoms


Signs and symptoms of diphtheria usually begin two to five days after a person gets infected. They may include:

In some people, infection with diphtheria-causing bacteria causes only a mild illness. These people may have no obvious signs or symptoms. Infected people who do not know they have diphtheria are called carriers of diphtheria, because they can spread the infection without being sick themselves.

Cutaneous diphtheria


A second type of diphtheria can affect the skin. This type of diphtheria is called cutaneous diphtheria. It causes pain, redness, and swelling on the skin, like other bacterial skin infections. People with cutaneous diphtheria may get ulcers, covered by a gray membrane, on their skin.

Cutaneous diphtheria is more common in tropical climates. However, cutaneous diphtheria also happens in the United States, especially among people with poor hygiene who live in crowded conditions.



Diphtheria toxin is produced by C. diphtheriae only when infected with a bacteriophage which integrates the toxin-encoding genetic elements into the bacteria.[2][3]


  1. "A Fresh Shot". Policy Exchange. Retrieved 2023-10-20.
  2. Freeman, Victor J (1951). "Studies on the virulence of bacteriophage-infected strains of Corynebacterium diphtheriae". Journal of Bacteriology. 61 (6): 675–688. doi:10.1128/JB.61.6.675-688.1951. PMC 386063. PMID 14850426.
  3. Freeman VJ, Morse IU; Morse (1953). "Further observations on the change to virulence of bacteriophage-infected avirulent strains of Corynebacterium Diphtheriae". Journal of Bacteriology. 63 (3): 407–414. doi:10.1128/JB.63.3.407-414.1952. PMC 169283. PMID 14927573.