AMERICAN PUBLIC HEALTH ASSOCIATION.

LOMB PRIZE ESSAY.

"Disinfection and Individual Prophylaxis Against Infectious

Diseases."

BY GEORGE M. STERNBERG, M. D., Major and Surgeon U. S. Army.

Disinfection and Individual Prophylaxis Against Infectious Diseases.

INTRODUCTION.

Definition. We are met at the outset by a difficulty growing out of the fact that the word disinfection, as commonly used, has a very different signification from that to which certain recent authors would restrict it. Thus the Committee on Disinfectants of the American Public Health Association defines a disinfectant as an agent capable of destroying the infective power of infectious material." (1). In the preliminary report of this committee the reasons for restricting the meaning of the word within the limits justified by its etymology, and of our knowledge of the nature of "infectious material," are very clearly stated, as follows:

"The object of disinfection is to prevent the extension of infectious diseases by destroying the specific infectious material (1.) The Medical News, Phila., Jan. 24, 1885, p. 87.).

which gives rise to them. This is accomplished by the use of disinfectants."

"There can be no partial disinfection of such material: either its infecting power is destroyed, or it is not. In the latter case there is a failure to disinfect. Nor can there be any disinfection in the absence of infectious material. * * * * *

"Popularly, the term disinfection is used in a much broader sense. Any chemical agents which destroys or masks bad odors, or which arrests putrefactive decomposition, is spoken of as a disinfectant. And in the absence of any infectious disease it is common to speak of disinfecting a foul cess pool, or a bad smelling stable, or a privy vault.

This popular use of the term has led to much misapprehension, and the agents which have been found to destroy bad odors -deodorizers, or to arrest putrefactive decomposition-antiseptics -have been confidently recommended and extensively used for the destruction of disease germs in the excreta of patients with cholera, typhoid fever, etc.

"The injurious consequences which are likely to result from such misapprehension and misuse of the word disinfectant will be appreciated when it is known that recent researches have demonstrated that many of the agents which have been useful as deodorizers, or as antiseptics, are entirely without value for the destruction of disease germs.

"This is true, for example, as regards the sulphate of iron or copperas, a salt which has been extensively used with the idea that it is a valuable disinfectant. As a matter of fact, sulphate of iron in saturated solution does not destroy the vitality of disease germs, or the infecting power of material containing them. This salt is, nevertheless, a very valuable antiseptic, and its low price makes it one of the most available agents for the arrest of putrefactive decomposition in privy vaults, etc.

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Antiseptic agents also exercise a restraining influence upon the development of disease germs, and their use during epidemics is to be recommended when masses of organic material in the vicinity of human habitations cannot be completely destroyed, or removed, or disinfected.

"While an antiseptic agent is not necessarily a disinfectant, all disinfectants are antiseptics; for putrefactive decomposition is due to the development of "germs" of the same class as that to which disease germs belong, and the agents which destroy the latter also destroy the bacteria of putrefaction, when brought into contact with them in sufficient quantity, or restrain their development when present in smaller amounts.

"A large number of the proprietary disinfectants,' so called, which are in the market, are simply deodorizers or antiseptics of greater or less value, and are entirely untrustworthy for disinfecting purposes." (1)

(1) The Medical News, April 18th, p. 425.

The offensive gases given off from decomposing organic material are no doubt injurious to health; and the same is true, even to a greater extent, of the more complex products known as ptomaines, which are a product of the vital-physiological-processes attending the growth of the bacteria of putrefaction and allied organism. It is therefore desirable that these products should be destroyed; and, as a matter of fact, they are neutralized by some of the agents which we recognize as disinfectants, in accordance with the strict definition of the term. But they are also neutralized by other agents-deodorants-which cannot be relied upon for disinfecting purposes, and by disinfectants, prop. erly so called, in amounts inadequate for the accomplishment of disinfection. Their formation may also be prevented by the use of antiseptics. From our point of view the destruction of sulphuretted hydrogen, of ammonia, or even of the more poisonous ptomaines, in a privy vault, is no more disinfection than is the chemical decomposition of the same substances in a chemist's labratory. The same is true as regards all of the bad smelling and little known products of decomposition. None of these are "infectious material" in the sense in which we use these words; that is, they do not, so far as we know, give rise directly to any infectious disease. Indirectly they are concerne 1 in the extension of the epidemic "filth diseases," such as cholera and yellow fever, and of the fatal endemic "filth diseases," such as typhoid fever and diphtheria, which in the long run claim more victims than do the pestilential maladies first named. This because persons exposed to the foul emanations from sewers, privy vaults, and other receptacles of filth, have their vital resisting power lowered by the continued respiration of an atmosphere contaminated with these poisonous gases, and are liable to become the victims of any infectious diseases to which they may be exposed. Moreover, the accumulations of filth which give off these offensive gases furnish pabulum upon which certain disease germs thrive; and it may happen that the bad smelling air carries something worse than the poisonous gas which makes its presence known by the offending sense of smell. It may waft to our nostrils infectious particles which are beyond recognition by any sense, unless it be the sense of sight with the aid of a good microscope.

We desire, moreover, to have it fully understood that in restricting the meaning of the term disinfectant within the limits given by the definition of the Committee on Disinfectants of the American Public Health Association, we do not wish to limit the practice of "disinfection" recognized by many intelligent per

sons,

Littre, in his Dictionary of the French Language, defines disinfectants as "substances which destroy, chemically, bad odors." Vallin, the author of the best modern treatise upon Disinfec tion and Disinfectants," says:

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"From a scientific point of view there is perhaps an imp opriety in introducing into the idea of disinfection the suppression of

odors which offend the sense of smell. The bad odor in itself is not injurious; it is an epiphenomenon, which does not necessarily give the measure of the hurtful properties of the air, or of any substance whatever. The public, unacquainted with medicine, has an unfortunate tendency to judge of insalubrity by the bad odor; the absence to this gives it a deceitful security; when they are masked by any device it (the public) believes that all danger has been removed. Nevertheless it is necessary to avoid violating the ordinary sense of words. An atmosphere which does not in the least offend the sense of smell may certainly be insalubrious, and engender the gravest maladies; but the fetid or disagreeable odors may reveal the presence of injurious principles of toxic gases, or of organic matter in decomposition. We should not too much diminish the importance of these offensive odors in the eyes of the public; every thing which smells badly is to be suspected." (1.)

We agree with Prof. Vallin, that the bad odors should arouse suspicion and lead to the use of deodorants, or of antiseptics, or of disinfectants, if required; but let us not leave the public to suppose that when the bad odors have been neutralized the offensive material has been disinfected. Let us rather instruct the public that to deodorize and to disinfect are not the same thing, and that deodorant and disinfectant are not synonymous terms. For our part we prefer to "violate the ordinary sense" of the word, and to restrict its signification within such limits as will prevent confusion, and, what is far worse, the reliance upon inefficient methods for the destruction of infectious material.

In the present essay we shall use the words disinfection and disinfectant, in accordance with the definition of the committee on disinfectants already given. But, inasmuch as this is intended to be a practical treatise for popular use, we shall also give, in the proper place, directions for the proper use of deodorants and of antiseptics, so that "disinfection" in the broad sense of the word's common usage may be fully considered.

Tests of Disinfection. What means have we of proving that the infective power of infectious material has been destroyed?

Evidence of disinfection may be obtained (a) from the practical experiments-experience of those engaged in sanitary work; (b) by inoculation experiments upon susceptible animals; (c) by experiments directly upon known disease germs.

(a). It is a matter of common experience that when a room has been occupied by a patient with an infectious disease, such as small-pox, scarlet fever, or diphtheria, susceptible persons are liable to contract the disease weeks or even months after the patient has been removed from it unless in the meantime it has been disinfected. But the non-occurrence of subsequent cases cannot always be taken as evidence that the means of disinfectio resorted to were efficient. Negative evidence should be receive

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(1) Op. Cit., p. 2.

with great caution. In the first place, the question as to whether susceptible individuals have been fairly exposed in the disinfected room must be considered. Then it must be remembered that susceptible persons do not always contract a disease, even when they are exposed in a locality known to be infected. A further difficulty in estimating the value of evidence obtained in practice arises from the fact that, in connection with the special means of disinfection resorted to, such as fumigation, hanging up clothes saturated with a disinfecting solution, etc., it is customary to resort to additional precautionary measures, such as washing surfaces with soap and hot water, white-washing plastered walls, and free ventilation. It is apparent that under these circumstances it would be unsafe to accept the fact that no other cases occurred in a room treated in this way, as evidence that the particular disinfectant used is efficient for the destruction of the infectious agent of the disease in question. The fond mother who attaches a charm to the neck of her child to protect it from evil, also takes the precaution of guarding it from contact with other children who are sick with any infectious disease. If her child fortunately grows to manhood or womanhood without having suffered an attack of scarlet fever or diphtheria, she may imagine that her charm has protected it, but the evidence upon which her faith is founded is not of a nature to convince those who are familiar with scientific methods of demonstration. "Well educated" persons are often ready to testify in favor of methods of disinfection, or of treatment, upon evidence which, from a scientific point of view, has no more value than that which the fond mother in question has to offer in favor of the little bag containing camphor or assafoetida, or some other charm of equal value, which she has attached to her child's neck to keep it from catching scarlet fever or diphtheria at school. On a par with these charms, so far as disinfection is concerned, we may place the saucer of chloride of lime which it was formerly the fashion to place under the bed of a patient sick with an infectious disease, the rag saturated with carbolic acid, or with chloride of zinc, suspended in the sick room, and even the fumigations with burning sulphur, as sometimes practised by those unfamiliar with the evidence as to the exact value of this agent, and the conditions necessary to insure successful disinfection with it.

Chloride of lime, sulphurous acid gas and carbolic acid are among our most useful disinfecting agents, but disease germs are not to be charmed away by them any more than by a little bag of camphor.

Having pointed out the fact that negative evidence, in a restricted field of observation, must be accepted with great caution in estimating the value of disinfectants, we hasten to say that the combined experience of sanitarians, derived from practical efforts to restrict the extension of infectious diseases, is of the greatest value, and that this experience is to a great extent in accord with the results of exact experiments made in the laboratory.

(b). Inoculation experiments upon susceptible animals, made