Disease transmission

“ Persons suffering with serious disease of a character communicable to others by contagion or by hereditary transmission.
Many people wonder why it is that diseases are so much more numerous and varied in modern times than in the earlier ages of the race. There has been an evident increase within a few centuries. While there are, undoubtedly, numerous influencing causes, one which cannot be overlooked is the hereditary transmission of disease, which preserves those disorders which already exist, and adds new ones which originate from new exciting causes. ”

“ Surely the places where dangerous infectious diseases are constantly propagated on a gigantic scale, and disseminated therefrom into the bodies of millions of animals and mankind, should be the very possible or probable source of epidemic disease. ”

“ There are no epidemical nor contagious diseases that attack every person who breathes the same air, or that is in contact with the infection, else whole regions would be depopulated. The habit must be graduated, or adapted, for the reception of a disease. ”

“ I have said that our knowledge in this direction has, even in the last two or three years, made enormous strides, and it is now almost a matter of certainty that all contagious or infectious disorders, as well as many others, are but the expression of the fact that minute living bodies have made a resting-place for themselves in or upon other living tissues; and that the development of the phenomena of these morbid states is but an indication of their presence and reproductive activity—either as cause, or as an accompaniment of these disease manifestations. ”

“ We know that the agents responsible for infectious diseases are specific minute organisms which must be present in the system to produce the disease in question, and that these micro-organisms are conveyed from place to place by infected persons, by intermediaries, on articles to which they have attached themselves, in contaminated food, in drinking-water, and in many other ways. ”

“ This enormous mass of disease furnishes ample material for infection on every side. A most infinitesimal germ, invisible, impalpable, would suffice to infect a single human body, and that body might suffice to infect very many others. ”

“ In like manner, when several members of a family contract tuberculosis, diphtheria, or measles, do they not get the disease because they all lived in the same manner and were exposed to like influences, instead of through contagion or infection with germs? Disease is sometimes spread, however, through the contagion of fear and suggestion. ”

“ In a common source epidemic, as where members of a population contract a non-contagious disease from a poisoned well, the disease spreads only by exposure to the common source. If one eliminates the source, or closes the contaminated well, the epidemic is stopped. ”

“ Investigators have studied the conditions in which these infective agents live and the manner in which they are disseminated, they have discovered methods of determining the nature of the disease in a very short time, and they have come to recognize the danger of coming in contact with germ-bearers, that is, with persons, healthy or convalescent, who have these micro-organisms in their systems without being themselves sick. ”

“ In this manner they cause the particular symptoms that are characteristic of a special infectious disease. Why is it that some persons, on exposure to an infectious disease, contract the malady while others similarly exposed do not? ”

“ At the beginning it is not possible to determine to which particular germ the distress of the patient is due, and probably the continued prevalence of these diseases is chiefly owing to the fact that in the early stages and in mild cases throughout, the sufferer is allowed to be at large with every opportunity for spreading the disease. ”

“ Every epidemic that sweeps through our communities is a testimony to the crying need of education in regard to such simple facts as the source of infectious material, the methods of its distribution, and the means of rendering it harmless.
PREVENTION IN INOCULATION. It has long been recognised that in most cases recovery from one attack of a contagious disease renders an individual more or less immune against a second attack. It is unusual for an individual to have the same contagious disease twice. ”

“ The word infection is applied to the vehicle by which a malady is transmitted from one person to another by the air, and with or without actual contact. The type of infectious disease is small-pox, and this is also, as is well-known, a highly contagious complaint. Scarlet-fever, measles, whooping-cough, mumps, etc., are likewise both contagious and infectious, and make up the class of disorders popularly known as diseases which are "catching." ”

“ It will doubtless be generally acknowledged that endemic and epidemic diseases depend upon some unknown agents, having their source in malarious districts, and being capable of assuming either a contagious or non-contagious character, according to circumstances. ”

“ Facts such as these help us to understand the production and propagation of disease through the medium of an infected atmosphere, whether on a large scale, as in the case of an epidemic which rapidly extends over a nation or a continent, or on a small scale, in the sick chamber, the dissecting room, the church, and the church-yard. ”

“ We have now reached a phase of this question when it is of the very last importance that light should once for all be thrown upon the manner in which contagious and infectious diseases take root and spread. To this end the action of various ferments upon the organs and tissues of the living body must be studied; the habitat of each special organism concerned in the production of each specific disease must be determined, and the mode by which its germs are spread abroad as sources of further infection. ”

“ In the latter, the name of the man, date of admission, and nature of disease, is placed over the bed of each patient, which in any contagious disease gives timely warning to any one fearing infection. ”

“ In all epidemics which increase to such a degree as to become contagious, it is of importance to distinguish which of these causes are the more powerful, the predisposing or epidemic causes, which originate the proneness to the disease, or the proximate causes, among which, in the generality of cases, contagion is the most prominent. ”

“ A few brief observations on the control and prevention of infections diseases, such as small-pox, measles, scarlet fever, typhus fever, typhoid fever, cholera, &c.
The above-mentioned diseases are capable of being transmitted from those who are infected to those who are not. It is at once cheering and obligatory to know that the spread of these infectious diseases depends upon certain specific conditions, and that these conditions are primarily within the control of man. ”

“ The contagious disease, spreading from the head to the members—from the Pope to lesser prelates—has spread far and wide, so that scarcely any one is to be found who does right, and who is free from infection. ”

“ The information at hand strongly indicates that apparently healthy individuals may transmit the infection, but the wide distribution of the disease, with multiple possible sources of infection for each individual, and the relative insusceptibility of experimentally exposed individuals has made it impossible so far to answer these questions satisfactorily. ”

“ Infectious disease continue to dominate the health scene in the less developed parts of the world. Recently in more educated, countries, incidence of communicable disease have shown dramatic fall in the last 50 years. ”

“ The nebulæ before Lord Ross's discovery were to the astronomer what the materies of epidemic and infectious disease are to medical men. In the absence however of a giant microscope to reveal such great truths, we may yet dimly shadow them by the light of our reason. It was predicted in 1849 that minute vegetable germs, in all probability all of the same type, were the agents producing epidemic and infectious disease. ”

“ Each infections disease is caused by a district type of germ and virus which is too small to be seen with human eye, but can be seen with the help of a powerful microscope. An Infection disease becomes a community problem because its prevention and control require the team work of health workers and community. ”

“ If these germs, however, are conveyed to another person, who has never had the disease, or whose tissue is not immune, they will immediately resume their full activity and virulence, and will establish the disease, frequently in its most violent form, in the person so infected. ”

“ Not a few, however, of their most mortal maladies are the production of contagion, infection, and other like causes, all exercising a general tendency to disease difficult to define and impossible to avoid. ”

“ Loathsome contagious diseases include those whose presence excites abhorrence in others, and which are essentially chronic, such as favus, ringworm of the scalp, parasitic fungus diseases, Madura foot, leprosy and venereal disease. Dangerous contagious diseases are such as trachoma, filariasis, hookworm infection, amœbic dysentery, and endemic hematuria. ”

“ The theory is, that any contagious disease can be eradicated; or, at all events, limited within a very slender area; and that various diseases are in reality contagious, such as typhoid fever and consumption, where the ordinary medical and general mind does not admit the fact of the contagiousness. If we resort to the primitive processes of counting noses, or listening for the largest amount of shouting, we shall decide against the theory ”

“ For the extension of infection from one individual to another the infecting organisms must in some way be transferred. The most important of the conditions influencing this are the localization of the disease and the character of the infectious organisms, particularly with regard to their resistance to the conditions met with outside of the body. The seat of disease influences the discharge of organisms; thus, if the disease involve any of the surfaces the organisms become mingled with the secretions of the surface and are discharged with these. ”

“ It is difficult, perhaps, to bring many instances, in which the germs of disease have lain dormant for a lengthened period, because many may take exception to them, from the fact, that sporadic cases of {89}most epidemic and infectious diseases, are rarely absent from any country in which those diseases have become indigenous, and these cases may be said to be the foci whence originates the epidemic constitution of the air ”

“ Remember that we and the disease germs are both cells; and that, if they are numbered by millions, we are by billions; and that we are made up of far the older and the tougher cells of the two. Except in a few of the most virulent and deadly of fevers, like the famous "Black Death," or bubonic plague, and lock-jaw, or tetanus, ninety-five times out of a hundred when disease germs get into our bodies, it is our bodies that eat up the germs instead of the germs our bodies. Keep away from disease germs all that you reasonably and possibly can ”

“ First, that they are contagious and absolutely dependent upon a living germ, whose spread can be prevented; and secondly, and practically even more important, that more than half the deaths from them are due, not to the disease itself, but to complications occurring during the period of recovery, caused, for the most part, by gross carelessness on the part of the mother or nurse. ”

“ Determining why susceptibility to a special disease in a particular case exists will constitute the greatest line of advance for the understanding and prevention of disease, and so the perfection of public health. In the last influenza epidemic countless physicians were puzzled by the spectacle of men and women in the pink of condition carried off in twenty-four hours while puny associates were either passed over, or pooh-poohed their colds. Pathologists have spent their energies fruitfully upon the infectious causes of disease, the microbes and parasites especially. ”

“ Contagious matter is lodged in goods of a loose and soft texture, which being packed up, and carried into other countries, let out, when opened, the imprisoned seeds of contagion, and produce the disease whenever the air is disposed to give them force, "otherwise they may be dispersed without any considerable ill effects." ”

“ Forewarned is forearmed, and it has been found that to know the cause of a disease is a long step toward avoiding it. As some of our contagious and epidemic diseases have been studied in the light of bacteriological knowledge, it has been found possible to determine not only their cause, but also how infection is brought about, and consequently how contagion may be avoided. ”

“ Lastly, I can conceive, and believe, that there is another and less directly-acting set of conditions influencing the distribution of disease conditions which as yet have been ignored by epidemiologists, but which, it seems to me, must have an important bearing on this subject. Disease germs, their transmitting agencies, or their intermediate hosts, being living organisms, are, during their extracorporeal phases, necessarily competing organisms, and therefore liable to be preyed upon or otherwise crushed out by other organisms in the struggle for existence. ”

“ In contagious diseases, infection proceeds chiefly from personal contact with a diseased person or objects that have been touched by him. In malarial diseases there is no danger from personal contact; the disease resulting clearly from a poisoned atmosphere. ”