This disease spreads mainly through droplet infections, but fomites, infected milk and food also transmit this disease. It is caused by Coryne bacterium diphtheria. The bacteria gets killed by heat and sunlight.

The incubation period is fairly short usually varying from 2-5 days. It is an acutely infectious disease characterized by fever, cough and the formation of a false, grey white membrane on the mucous membrane of throat. The nose and larynx may also get affected. The bacteria produces toxin which is injurious to the nervous and cardiac systems. This toxin is absorbed by the blood. In severe cases swallowing is difficult and choking may cause death.

This disease is more common in children between 3-5 years of age. Low resistance accompanied by insanitary and cramped living conditions is yet another predisposing factor. The disease occurs in winter months and if neglected can be fatal.

An attack of diphtheria does not provide lasting immunity. Immunity can be conferred on small children by giving D.P.T. vaccine. The diphtheria vaccine is prepared from the toxin produced by the Coryne bacterium diphtheria. The toxin induces the production of antibodies in blood.