Diphtheria is an acute respiratory infection caused by the diphtheria bacterium, Corynebacterium diphtheriae and its toxin. This is a serious infection with a high mortality rate, even in Western Europe.

The bacteria multiply on the lining (mucous membrane) of the throat, nose or larynx, where they divide and excrete a poisonous substance or toxin. The bacteria and the toxin destroy the mucous membrane, so that a thick coating is formed and the patient develops a serious inflammation of the throat. The membranous coating in the throat can become detached and obstruct the airways, making breathing difficult and sometimes causing asphyxiation. The bacterial toxin penetrates the body and can lead to damage of the cardiac muscle and the nervous system.

The incubation period, which is the time that elapses between a person being infected and the disease developing, is usually two to five days.

Local symptoms consist of a sore throat, coughing and breathing difficulties. When the disease infects the skin it causes crusty scabs, similar to impetigo.

General symptoms manifest themselves as a slight rise in temperature, limpness and fatigue. In weeks two to six of the illness, damage to the heart and nervous system may be observed in the form of irregularities of the heart beat and paralysis. In the worst cases, this may cause serious disturbances in cardiac rhythm, and possibly cardiac arrest.

Mortality in poorer countries is high, up to 30 to 40 per cent, while in Western countries it is between 5 and 10 per cent, partly because the disease may be confused in the early stages with other infections, which results in treatment being started too late.