Infectious disease of the throat which can be serious in children. It is caused by the diphtheria bacillus, which establishes itself in the mucous membrane of nose and throat, producing a greyish-white false membrane on the tonsils. The disease is dangerous because this false membrane can cause suffocation, and the toxins produced by the bacillus can lead to serious complications elsewhere in the body. The infection is contracted via the air (droplets) and the incubation period lasts for a few days. Nasal diphtheria starts like a common cold, with a slight fever. After a few days there may be blood in the nasal discharge, particularly in infants. Throat diphtheria shows as severe pharyngitis, with high fever and a red and swollen throat. A grey false membrane appears on the tonsils, and the glands of the neck are swollen. The most feared form is diphtheria of the larynx, causing hoarseness, a barking cough and constriction. Toxins cause complications in diphtheria after one to six weeks, and can affect the heart muscles and the nerves of the soft palate and the eye muscles. Generally they can be treated successfully, in the first place by isolation and then by the use of anti-diphtheria serum (passive immunization) to prevent the spread of dangerous toxins. The patient must be observed constantly, and may need tracheotomy to avoid suffocation. The most important measure is active immunization of healthy children, which has by now almost wiped out the disease.