Epidemiology

Epidemiology (from Greek epidemia-epidemic and logos-teaching), the doctrine of epidemics, a science whose task is to study the laws of emergence, development, and extinction of epidemics. In this sense, the word E. has completely replaced the old word 'loimology,' which formerly in a broader sense meant the doctrine of contagious diseases, and in a narrower sense-the doctrine of plague. On the basis of studying the laws of epidemic movement, E. makes certain practical conclusions, consisting in the development of rational measures to combat the spread of contagious diseases. E., like other sciences, arose and developed historically from direct practical measures taken by people for the purpose of combating contagious diseases. All these practical measures, until they were systematically and critically processed by modern science, in accordance with various concepts of the essence of contagious diseases that prevailed in different historical epochs, in most cases were either simply absurd (burning of 'witches,' mystical rites, sacrifices) or were of a purely empirical, little rational character (e.g., inoculation of human smallpox into children for the purpose of protecting them from contracting it at a later age, used since ancient times in China, ancient Hebrew legislation prohibiting the consumption of certain types of meat to eliminate certain associated diseases, medieval 40-day quarantines to prevent the importation of plague into Europe, etc.). Among all the material of this period, we rarely encounter correct epidemiological views that have retained their significance to our day. A revolution in the field of E. occurred only in the second half of the 19th century, in connection with the establishment and scientific confirmation of the view that the basis of a contagious (infectious) disease always lies in the penetration into the human or animal organism of a specific causative agent of this disease. From this moment, the possibility was first opened to place the fight against contagious diseases on a rational basis, and moreover the extremely rich experience of the very successful development of anti-epidemic measures in a relatively short period made it possible to make a number of most valuable generalizations and discover a number of laws revealing the essence of the development of epidemics of individual infectious diseases, and by generalizing these particular laws to establish even more general laws of this science. Along with this, E. has accumulated an extremely rich factual material, concerning both the question of the transmission of infection from individual to individual, and the conditions of mass (epidemic) spread of infectious diseases. As a result, we can now speak in the present time of general E. as that part of the science that studies the most general laws of epidemics, and of private, or special E., which deals with the peculiarities of the epidemic spread of individual contagious diseases. Both parts of the science in turn are divided into 2 departments: one, studying the proper laws of epidemic development (theoretical), and the other, on the basis of establishing these laws, developing the most rational measures of anti-epidemic struggle (practical). Almost until the end of the 19th century, the so-called localist school enjoyed great popularity in E., at the head of which stood one of the greatest hygienists of the second half of the 19th century, Pettenkofer. Individual elements of his doctrine, more or less adaptable to modern views, are still supported by a few scientists (see Soil). Although the essence of this doctrine, which attempted to reduce epidemiological laws to local properties of the soil, turned out to be erroneous according to almost universal recognition, nevertheless in its time Pettenkofer's doctrine played a major useful role in the improvement of living conditions for a multitude of cities of Western Europe, since under its influence these cities received satisfactory conditions of their improvement, sewerage, and water supply. With the development of the microbiological view of the nature of contagious diseases, another scientific epidemiological school increasingly consolidated, the ideological inspiration of which is rightly considered another great German hygienist, R. Koch. This doctrine, which in general proceeded from the essentially correct view of the etiological (causal) connection of the moment of penetration of the microbe into the human organism and the fact of the latter's disease, however adopted a somewhat simplified scheme of this process. Called contagionist, Koch's doctrine considered that the penetration of the causative agent into the human organism is not only a necessary preliminary condition, but also a fully sufficient moment for the inevitable onset of the disease to follow. An in-depth study of the development of the infectious process in the human organism in connection with the reactive responses of the latter to the penetration of the causative agent into it and the conditions of mass (epidemic) spread of infectious diseases among the human population under different conditions, although in general confirmed Koch's original position, significantly clarified the understanding of this process, introducing into it a number of additional, previously completely unconsidered moments. The study of questions of susceptibility and immunity, the discovery of phenomena of bacillus-carriage and the role of higher animals (in particular rodents) and insects in the spread of contagious diseases, the modern understanding of the significance of social factors in the spread of epidemics, the discovery of a number of 'new' (previously unknown) contagious diseases, along with prospects and even real achievements on the path to eliminating a number of others-all these questions, worked out over the last 3-4 decades, represent a number of pressing problems that have opened before this science completely exceptional horizons both theoretical and practical.- Setting as its task the study of the laws of the spread of epidemics of contagious diseases and the development of measures to combat their spread, E. in its nature, content, and methodology differs significantly from most of the well-known practical 'medical' disciplines in the direct sense of this word (i.e., therapeutic). While the latter deal with the individual, E. always has in mind the collective, which is threatened by the spread of an epidemic in its midst, and the elimination of this threat is achievable only by measures covering the entire collective and to a large extent directed at the environment surrounding it. These peculiarities of E. force to qualify it as a science: 1) preventive, i.e., pursuing the goal of prevention, and 2) organizational, i.e., using as the basic method of its work organizational techniques. In the course of its organizational activity, E. also applies a number of special, developed by it technical anti-epidemic techniques, which include, for example, disinfection, vaccination, isolation of the sick, neutralization of healthy carriers of infections, etc. Both its practical and theoretical parts E. develops with the assistance of a number of related disciplines, among which microbiology, clinic and pathological anatomy of contagious diseases (see Infectious Diseases) play the greatest role, but along with them, sanitary statistics also plays an enormous role in the development of epidemiological problems. Accordingly, E. uses quite widely the basic methods applied in scientific research in general. The experimental method has found extremely wide and fruitful application in resolving a huge number of particular questions, the correct resolution of which has greatly contributed to the progress of E. This method is basically applied in the form of individual laboratory-bacteriological experiments on animals, in individual cases also on humans, in the latter case usually by experimenters on themselves or on their colleagues and other persons voluntarily offering themselves for this purpose. In resolving some questions, experiments of a physical (e.g., in studying the processes of so-called 'droplet' and 'dust' infection) or chemical (e.g., in studying disinfection processes) nature are also applied, etc. In recent times, a number of authors (Topley, Webster, Flexner, Neufeld, etc.) have developed a new method of mass laboratory experiment on animals, which has received the methodologically incorrect name 'experimental epidemiology.' It is self-evident that the basic phenomenon which serves as the object of study of E., namely the epidemic, i.e., the mass spread of a contagious disease among the human population, cannot in any way be reproduced in the form of an experiment. Therefore, E., along with the experimental method, also widely uses the method of observation in all those forms in which it can be applied to processes of a social order, to which epidemics developing in human society to a large extent belong. These include: 1) the statistical method, especially in its modern development (variation statistics) having reached very great accuracy; 2) the method of direct observation, in turn applied in the form of observation of the course of the epidemic as a whole, in the form of epidemiological examination of the focus, and finally in the form of observation of individual cases of infection.

Only the combined use of all the methods listed above ensured Epidemiology the enormous progress and practical achievements that characterize the history of this science over the last decades. But from this it is also clear how helpless researchers are in solving current epidemiological problems when they try to base their conclusions regarding epidemiological processes on the isolated application of only one method (this is most often observed in the form of exclusive use of either the experimental-bacteriological or the statistical method). Despite the significant successes of Epidemiology and its development into an extensive and practically important discipline in its own right, it has not yet found its proper place in the curriculum of higher medical schools. In foreign medical faculties, Epidemiology is often taught in the form of optional privat-docent, sometimes docent courses; only in some American medical schools are departments of Epidemiology organized. In the USSR, the first department of Epidemiology was organized in Odessa in 1920, and the first head of this department was Academician D. K. Zabolotny from 1920-22. This department developed a detailed curriculum and teaching methodology for Epidemiology. With the organization of san.-prof. faculties in the USSR, Epidemiology was included in the curriculum as a mandatory subject. The prevalence of Epidemiology as a practical discipline finding application in the system of health care organs is quite extensive both in other countries and in the USSR. Epidemiologists are an essential link in every reasonably developed san. organization; elements of epidemiological practical work in the form of vaccination, disinfection, etc. must constitute an integral part of the work of every, even the most primitive, health care cell, and the introduction of epidemiological, i.e., actively-operative and based on data of modern science, health-improving trends into the work of all bacteriological and therapeutic-prophylactic institutions (stationary and ambulatory therapeutic-prophylactic institutions, laboratories, malaria and Pasteur stations and points, etc.) constituted a generally recognized and important current task.

EPIDEMIC ENCEPHALITIS

534 The organs of scientific research work in the field of epidemiology in the USSR are a network of special institutes (for details, see Bacteriology): the Central Institute of Epidemiology and Microbiology in Moscow and over 35 similar institutes on the periphery within the RSFSR, 6 institutes of the same character in the Ukrainian SSR, 3 in the Transcaucasian SSR, 2 in the Byelorussian SSR, and one each in the Uzbek SSR, Turkmen SSR, and Tadzhik SSR. Periodical literature specifically dealing with questions of Epidemiology is represented in the RSFSR by three journals: 1) 'Journal of Epidemiology and Microbiology', published in Moscow from 1932 and being a continuation of the epidemiological part of the journal 'Hygiene and Epidemiology', published until 1931, from 1935 it began to be published under the name 'Journal of Microbiology, Epidemiology and Immunobiology'; 2) 'Bulletin of Microbiology, Epidemiology and Parasitology', published in Saratov; 3) The journal 'Medical Parasitology and Parasitic Diseases' in Moscow, mainly dealing with questions of malaria and helminthology; it is a continuation of the former 'Journal of Tropical Medicine'. In the Ukrainian SSR the journal 'Preventive Medicine' is published (since 1929 in the Ukrainian language). Many other journals devote space to individual epidemiological articles. (See also data on periodical literature in the articles Bacteriology and Infectious Diseases.)

L. Grimshe,»'. r.mi.