Read condition-specific symptoms and clinical context for Corynebacterium diphtheriae. The diphtheria bacterium: illness comes from a toxin that only some strains produce.
CDC describes diphtheria as any illness caused by a toxin produced by some strains of C. diphtheriae, and toxin production depends on a bacteriophage carrying the tox gene. Respiratory diphtheria is the most serious form, where a thick grey pseudomembrane of dead tissue can build up in the nose and throat; skin infection is a separate presentation. People can carry the organism without becoming ill and still pass it on. Throat illness resembling diphtheria was described in antiquity, long before the bacterium was observed in 1883.
CDC lists these symptoms for respiratory diphtheria and states that it usually takes 2 to 5 days for symptoms to appear after exposure.
Possible symptoms: Weakness; Sore throat; Mild fever; Swollen glands in the neck; Pseudomembrane in the nose or throat.
CDC lists airway obstruction, myocarditis, polyneuropathy and kidney failure among complications, and states that treatment for suspected respiratory diphtheria begins right away without waiting for test results.
CDC describes cutaneous diphtheria as infection of the skin by bacteria that make diphtheria toxin, and lists these symptoms.
Possible symptoms: Open sore or ulcer with a clear edge; Pain; Redness; Swelling; Rash with scales or peeling skin.
Skin sores have many causes. Laboratory testing identifies C. diphtheriae and whether the strain produces toxin.
CDC states that some people may become infected and have no symptoms, and WHO adds that they can still transmit the bacteria.
CDC states that some people may become infected and have no symptoms. WHO adds that some people may not develop disease manifestations but can still transmit the bacteria. PHAC notes the organism may be present in the nasopharynx or skin lesions for weeks to months, or even for life, in asymptomatic people, who can act as a reservoir. None of the symptoms listed above apply to this state.
Asymptomatic carriage is managed as a public-health matter rather than as diphtheria illness. Laboratory testing distinguishes carriage, and toxigenicity testing distinguishes toxin-producing strains.
Source check: 2026-09-19. Educational content; independent scientific review remains pending.