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Infection and Disinfection: According
This confusion of thought is now to a large extent cleared away. The contact infection theory may be said to be fully established. According to this theory the living bacteria, or germs, which cause contagious diseases are most commonly transmitted from a diseased to a well person within a comparatively short space of time, and through the medium of some solid object or liquid, rather than through the air. Two kinds, or types, of infection are loosely distinguished - direct and secondary. Direct infection is, in general, that which gives rise to new cases in families or on premises that have been previously free from disease. Indirect, or secondary, infection is that whereby a disease is communicated from a patient to his nurse or other attendant, or to other members of the same household. Direct infection is thought to occur chiefly through the contamination of the sources of water or milk supply, or by chance contact with persons in the early stages of a communicable disease, or those suffering from mild cases, or from healthy "carriers." Especial attention has also been directed of late to the part played by insects, especially the house fly, as carriers of disease. The bedbug, the body louse, the various species of fleas, mosquito and ticks have also been found to communicate the germs of disease from certain animals to man and from one person to another.
Direct infection may, and often does, occur from unavoidable accident. But secondary infection is invariably the result of ignorance or INFECTION AND DISINFECTION carelessness. The most usual vehicles of secondary infection are thought to be the bed covers or clothing of the patient; his handkerchief; his discharges; remnants of food and drink left by him on the tray, or the dishes or other utensils by means of which he is served; and the person or clothing of the nurse or other bedside visitors. The cardinal principle of preventive medicine is that secondary infection must and shall not occur. or According to the contact infection theory all the germs of disease by which healthy persons are infected had quite recent origin in the body of some diseased person. They left the patient through some of his discharges, as his sputum or excreta, possibly through perspiration, or in the case of smallpox, chickenpox, or scarlet fever, through the scabs or scaling of the outer surface of the body. Thence they were transmitted to the neighborhood of the infected person, through some fairly direct route, by the agency of solid bodies or liquids, and under conditions reasonably favorable to germ life. They then found their entrance into his body through some of its main orifices, usually by being breathed in or swallowed. When these essential principles are well understood and sufficiently considered, they will usually enable the responsible head of a family to trace a case of infection to its source. Steps may then be taken to avoid further infection and prevent the spread of the disease.
The open vault, sink drain, or accumulation of garbage or other filth, so located as to contaminate the soil or the sources of the water supply, and the flies or other insects which feed in and about them, may be compared to an unloaded gun. Their deadly possibilities are latent until they become infested (loaded) with the living germs of typhoid or other communicable diseases. Such germs are not the product of putrefaction.
They do not develop spontaneously in fecal or decayed matter such as night-soil, garbage, and kitchen slops.
Nor do disease germs multiply in such locations. Indeed, the bacteria which cause human diseases will ordinarily die out within a comparatively short time when deliberately added to such substances for the purpose of scientific investigation.
When a case of typhoid or other contagious disease occurs, through the pollution of the soil or water supply, or through the medium of flies, by contagion from an open vault or drain or similar nuisance, the real source is often overlooked and disregarded, because these nuisances have existed before the patient was taken sick and no one had previously been made ill by them. The explanation of science is that only at rare intervals and as a consequence of direct infection from some diseased person, do these nuisances become active sources of contagion and deadly menaces to the public health. The danger is that this may happen unknown to the responsible head of the family. The result may be an epidemic in which many lives are needlessly sacrificed. A good illustration may be found in a case reported by a milk inspector of a western city. An outbreak of typhoid was traced to the milk supply from a certain farm dairy.
On investigation it was found that two of the dairyman's children were convalescing from that disease. The family water supply used for drinking purposes and also for cleansing milk pails and other receptacles was a dug well in the farmer's yard. It was located not far from an outhouse of the open vault type. The milk inspector suggested that the well water might be contaminated from this source. The dairyman responded that this could not be the case because the water was clear, cold and tasteless. A few days later this farmer called up the milk inspector on the telephone and inquired if the germs of typhoid fever would make water pink. The inspector responded, No! but that if the well water was pink, it might be due to a quantity of red dye which he had poured into the vault of the outhouse. Later, the dairyman himself succumbed to typhoid fever. The milk supply from this dairy having been shut off, further spread of the disease among its patrons was prevented.
A practical suggestion may be drawn from this incident for cases where it is suspected that the source of drinking water may be contaminated from open vaults, drains or similar sources. A bushel or more of coarse salt may be deposited in the vault or drain and care taken to observe whether or not the water, especially after the next heavy rain, tastes in the least salty.
But, as the amount of salt that might be transmitted in solution through the soil may not be enough to be detected when diluted by the contents of a deep well, it is safer and better in all such cases to have a bacteriological test of the water made at the State laboratory. The commissioner of health in most States will forward on request a suitable bottle properly packed for mailing, with full directions how to select and forward the necessary sample. In some States such tests will be made free. But in any case the cost will hardly exceed that of a doctor's visit.
The result may be the saving of one or many lives.
The bacteria which cause germ diseases are parasites, that is, they do not normally occur in nature outside the bodies of men or other animals.