There are bad cases of diphtheria which the experienced physician can diagnose as soon as he enters the patient's room without even looking at the throat, but the lighter cases that are dangerous are not easily recognised. I have seen two children of a family in Washington attacked with a slight throat soreness after one child had died of diphtheria in the house. The cases of these two children would never even suggest diphtheria if that first child had not had the disease. Both these patients died within ten days of syncope without the formation of any membrane, but the diphtheria bacillus was present microscopically. To the moment of death there was nothing in the symptoms of these two children to show diphtheria to the naked eye. From a personal experience with more than 800 cases of diphtheria in hospitals and as a medical inspector, I feel certain that light attacks of diphtheria can not be diagnosed without the aid of the microscope.
The immunity mentioned above explains the fact that the Klebs-Loeffler bacillus is sometimes found in healthy throats, and the person that has such a throat is really more dangerous than a patient that is ill with diphtheria, because we cannot guard ourselves against him. School-children at times have what appears to be mere sore throat but which is really diphtheria in the naturally immune.
All cases of sore throat in school-children should be examined bacteriologically, but unfortunately the bacteriological examination for diphtheria is a complicated process which requires an expert bacteriologist and a laboratory. The cost of a laboratory fitted for this diagnosis alone is not great, but it is not easy to persuade small city governments that they need such plants.
The only resource, then, is to treat every suspicious case of sore throat as if the disease were really diphtheria, until a diagnosis is established as near the truth as possible. Children that are afflicted with throat inflammations should be kept from school. The people should be taught the necessity of isolation and disinfection; they should be warned against patent disinfectants, and told to ask competent physicians to advise them in disinfection.
Diphtheria is not directly caused by unhygienic surroundings. A disregard for hygiene disposes a child for infection if the child is exposed to the bacillus. The specific germ must be introduced into the patient's mouth or nostrils. When a child is infected with diphtheria the breath is not a medium of contagion. The sputum, spat out or coughed out, is a means whereby the disease is spread. The bacillus is in the patient's mouth and nostrils; it gets upon his hands by contact, upon eating utensils, upon whatever touches the mouth of the sick person. The bacillus does not float in the air of even the sick-room, except in those cases where dried sputum is stirred up by sweeping or attrition of other kinds.