Summary

• Diphtheria is an illness caused by toxigenic strains of Corynebacterium diphtheriae. It is endemic in many areas of the world and still occurs sporadically in the US.
• Important sites of infection are the respiratory mucosa (respiratory diphtheria) and the skin (cutaneous diphtheria). Rarely, the mucosa of the eye, ear, or genitals may be affected. The incubation period is typically 2 to 7 days, occasionally longer.
• Early intervention by administering antitoxin is key to preventing systemic manifestations of the disease, which can include respiratory and neurological symptoms, cardiovascular collapse, and death.
• Prompt administration of antitoxin is necessary to enable it to bind to and de-activate the free toxin in serum. Antitoxin cannot de-activate toxin once it has entered cells, which is signalled by the presence of mucocutaneous symptoms.
• Patients with respiratory diphtheria are placed in respiratory isolation (masks and standard measures such as hand-washing), and those with cutaneous diphtheria are placed in contact isolation (gloves and gowns), until cultures taken after cessation of therapy are negative.
• Asymptomatic carriers play an important role in disease transmission.