Over the centuries the development of human society has formed a special branch of scientific knowledge dedicated to the prevention and control of infectious diseases. History shows that in the course of its evolution, the damage to humanity from infectious morbidity exceeds by many orders of magnitude those from social and natural disasters. Specific terms have emerged that identify epidemics as infectious diseases with “black pages” in the life of human society. With the progress of historical progress, disparate scientific ideas have evolved into a science – epidemiology, which studies the patterns of the epidemic process, in the interests of preventing and combating infectious diseases.
With the expansion of prevention boundaries beyond infectious pathology, there was a need for a population approach in the study of not only infectious but also non-infectious diseases. At present, general principles and methodological bases of population study of all diseases have been formulated. The concept of non-infectious epidemiology has emerged. Therefore now it is lawful to allocate:
– epidemiology as a general medical science;
– epidemiology as a science about the epidemic process.
Epidemiology as a general medical science studies the causes, conditions and mechanisms of the formation of the morbidity of the population by analyzing its distribution across the territory, among different population groups and in time for the development of methods of disease prevention.
Definition of epidemiology as a science.
The epidemiology of infectious diseases studies the features of parasite-host interaction at the population level (epidemic process) by means of a system analysis of infectious morbidity and develops methods of influencing the epidemic process.
As a scientific discipline, epidemiology includes a set of theoretical, methodological and organizational principles for the justification and conduct of preventive and antiepidemic measures among the population. Theoretical basis of modern epidemiology are the teachings:
– about the epidemic process;
– about the natural focality of infectious diseases;
– self-regulation of parasitic systems;
– about the social and economic concept of the development of the epidemic process.
Epidemiology as a medical and biological discipline has a number of concepts corresponding to the general sections of other medical and biological sciences:
– the doctrine of the factors of the epidemic process (biological social and natural) corresponds to the etiology of the disease;
– a section of epidemiology about the mechanism of the development of the epidemic process – the pathogenesis of the disease;
– the manifestations of the epidemic process studied in the epidemiology – the clinic of the nosological form.
At the same time, along with a number of general concepts, the epidemiology of infectious diseases has strictly specific differences from clinical disciplines:
– in infectology the disease is studied, and in epidemiology – the incidence of this or that form;
– in the medical and biological disciplines the pathological process is considered, and in epidemiology the epidemic process;
– when studying a whole series of medical disciplines, first of all intuitive thinking is used, in contrast to epidemiology, where first of all, logical thinking is used.
The practical way out of the science of epidemiology is the development of the system:
– prevention of the incidence of infectious diseases of certain population groups;
– decrease in the incidence of the total population;
– elimination of individual infections on a global scale.
The variety of goals and practical tasks solved by epidemiology has determined the close connection of scientific discipline with a number of natural and medical and biological sciences. First of all, its connection with the sciences studying infectious pathology, such as microbiology, parasitology, a clinic of infectious diseases, is clearly traced. The epidemiological aspect of a comprehensive study of the problems of these scientific disciplines is an indispensable condition for modern scientific research. At the same time, in carrying out practical measures aimed at reducing infectious morbidity, data from microbiology, parasitology and other sciences are used. Thanks to population epidemiological methods of research, medicine was enriched with the knowledge necessary for the prevention of many non-communicable diseases. In modern conditions, epidemiological studies are widely used to study the risk factors of cardiovascular, oncological and endocrinological diseases and various infectious pathologies.
Due to the implementation of common goals, the traditional links of epidemiology with hygiene are being built up, mutually enriching these preventive sciences. In modern conditions, in connection with the wide introduction of electronic computing in all types of human activities, general issues of epidemiology with informatics, medical and biological statistics and mathematics are revealed. Complex research in these areas allows to obtain objective and integral characteristics of infectious morbidity, thereby more purposefully to influence the epidemic process. The connection between epidemiology and organizational and medical disciplines is traditional. The links between epidemiology and the complex of sciences studying the epizootic process are strengthened, with such branches of biology as ecology, genetics, etc.
The epidemic process is determined not only by the biological and ecological relationships between the pathogen and the organism. It develops and manifests itself in the concrete conditions of the existence of human society. Therefore, the materials of the social sciences give epidemiology an opportunity to link the development of the epidemic process with the entire set of social conditions in which the epidemic process occurs, spreads and stops. The development of measures to reduce the infectious morbidity rate constitutes an important section of epidemiology, which is directly related to state legislation.
Thus, despite the synthetic nature of epidemiology, in the process of the evolution of human society this scientific discipline has its own specific concepts and laws peculiar to any science.
Main sections of epidemiology.
Modern development of epidemiology made it possible to identify the following sections in the composition of this scientific discipline:
- Teaching about the epidemic process:
In this section, the regularities of the epidemic process among the population in different conditions and regions of their residence are studied. Methodically, this teaching is divided into the following constituent elements:
- a) factors of the epidemic process (biological, social, natural);
- b) mechanism of development (source of infection, mechanism of transmission, susceptibility of the organism);
- c) the manifestation of the epidemic process (intensity and distribution of infectious morbidity).
- Means and methods of antiepidemic care of the population.
To ensure sanitary and epidemiological welfare of the population
hygienic and anti-epidemic measures are carried out, which are carried out with the help of certain means and are used according to specific methods. In order to optimize the measures for antiepidemic care of the population, they are grouped in accordance with the main sections of the doctrine of the epidemic process:
- a) measures aimed at neutralizing sources of infection;
- b) activities aimed at breaking the transmission mechanism;
- c) measures aimed at reducing the susceptibility of the host.
- Epidemiological diagnosis:
Knowledge of the complex of measures for antiepidemic care of the population is insufficient to ensure sanitary and epidemiological well-being. Depending on the structure of infectious diseases, the characteristics of the epidemic process in the different conditions of life, way of life and activity to the population should identify the main areas of preventive and anti-epidemic work. The choice of targeted measures for antiepidemic care of the population in specific conditions is carried out using epidemiological diagnostic methods. The main methods include:
- a) Retrospective epidemiological analysis. In view of its results, long-term planning of measures for antiepidemic care of the population is carried out and the quality of the work carried out earlier on the prevention and control of infectious diseases is assessed.
- b) Operative epidemiological analysis. This method of epidemiological diagnosis is a logical continuation of the retrospective epidemiological analysis. Operative epidemiological analysis
includes a dynamic assessment of the status and trends of the epidemic process, and specifies the direction of prevention.
- c) Epidemiological examination of foci of infectious diseases. Allows to establish the causes and conditions for the formation of an epidemic focus and to select the main measures for its elimination
- d) Sanitary-epidemiological investigation and sanitary-epidemiological surveillance. The main task of this method of epidemiological diagnosis is the timely assessment of the likelihood and possible routes of infection transmission from different population groups and other contingents and from epizootic foci.
- Organization of measures for antiepidemic care of the population. This section includes a substantiation of a rational division of responsibilities between officials, the establishment of rights and responsibilities of performers, the foundations of their relationship with a view to ensuring successful cooperation in the task of ensuring sanitary and epidemiological
well-being of the population. The following issues are considered:
- a) organizational and staff structure of sanitary-epidemiological institutions – TSGSEN;
- b) a functional system for the organization and management of antiepidemic measures;
- c) peculiarities of the organization of anti-epidemic services to the population in different conditions.
- Private epidemiology. It presupposes a purposeful study of the epidemiological features of a diverse infectious pathology relevant for these population groups.
- Biological weapons and biological protection. This section examines the characteristics of the damaging effect of biological diversity, the assessment of the bacteriological situation and the system of measures for biological protection and the elimination of the consequences of its use.
Main stages of epidemiology development
In the process of evolutionary development, epidemiologists can distinguish the following stages: bacteriological, bacteriological, scientific epidemiology, modern epidemiology.
- Addobiological (Until the last quarter of XIX).
Prerequisites for its occurrence are a number of issues, the main of which is: Why do epidemics evolve at certain times, in certain territories, under certain conditions?
The concept of the epidemic constitution of the places and years of Hippocrates and Seidenheim.
Explanation: 2 theories.
a) The theory of “miasma” – Hypocrates, Sidengem (1627-1689). Epidemics arise as a result of the penetration into the human body of miasms (gr.miasma – filth) – “pathogenic substances” of cosmo-telluric origin, i.e. arising in the air or in the bowels of the earth at a particular time. and not transferable from person to person.
Later, the famous English physician of the seventeenth century Thomas Seidenheim, a follower of miasmatics, developed this doctrine and wrote it in the following form:
“There are various constitutions of those or other years that do not depend on heat, cold, dryness or moisture, but rather on an incomprehensible change that is hidden from us in the bowels of the earth, as a result of which the air will become contaminated by evaporation, predisposing the human body to this or that infection while the given constitution lasts, after the lapse of several years disappearing and replaced another ».
The significance for modern epidemiology of these theories lies in the brilliant foresight: the theory of natural foci of diseases.
- b) The theory of “contagion” – Frakastro (1478-1553), Samoilovich (1724 -1810).
Epidemics arise from the infection of people with contagia (Latin contagium – infection), transmitted from the patient to a healthy way of contact.
Importance for modern epidemiology: foreseeing the infectious nature of diseases.
- Bacteriological (70-90 years of the Х1Х century). The greatest microbiological discoveries of L.Paster, R.Koh, P.Erlich, D.Ivanovsky, I.Mechnikov, Stallibras and many others led to a revolution in epidemiology and medicine in general. A new medical science emerged-the general doctrine of contagious diseases with bacteriology and the clinic-infectology.
The logical conclusion of the bacteriological stage in the development of epidemiology was the simplified theory of the three factors of Stallibrus: the seed, the sower, the soil, that is, the microbe, the external environment and the organism.
A positive effect is the justification of many preventive and antiepidemic measures: isolation, vaccination and disinfection.
The negative effect – the “black days of epidemiology”, when excessive interest in the microbiological side in the study of infectious diseases, caused significant damage to pathogenetic and epidemiological studies.
- Scientific epidemiology (first quarter of the XX century). The prerequisites for the emergence were the questions of how and how the causative agents of infectious diseases (eg typhoid fever) are preserved as biological species?
The explanation of these facts was the work of Russian scientists:
- a) The doctrine of the mechanism of transfer LV Gromashevsky.
Driving forces of the epidemic process are the 3 links of the epidemic chain. Infinitely prolonged circulation of the pathogen is achieved by the stereotyped response of the susceptible organism and by the invariability of the pathogenicity of the pathogen. The change in characteristics is the death of the system.
However, questions remained: What is happening and how long are pathogens persisting not transmitted from person to person (eg plague)?
The explanation for this was the long scientific research of E. N. Pavlovsky:
- b) The doctrine of the natural focality of E. N. Pavlovsky. The totality of biotic and abiotic elements of the environment provides an infinitely long circulation of pathogens in natural foci, regardless of man and his economic activities. Man is a dead-end branch for many zoonotic diseases.
- Modern epidemiology (80th years of XX century).
Before epidemiology, the task was: how are the pathogens of highly-known anthroponoses (influenza, measles) preserved? This was explained by VD Belyakov’s Theory of Self-Regulation of Parasitic Systems.
The essence of the theory of self-regulation:
1) The interacting parasite / host system is initially heterogeneous in terms of virulence (parasite) and susceptibility (host).
2) During the epidemic process, these characteristics are constantly changing.
3) The interaction takes place in the constantly changing activity of the social and natural factors of the epidemic process.
4) Self-restraint of populations causes 4 phases of the epidemic process, which ensure the expansion of the area of the pathogen circulation and the conservation of both biological species and parasite and host (the phase of reservation, the phase of the epidemic strain, the phase of epidemic spread, the phase of the inverse development).
The history of mankind was constantly accompanied by epidemics of infectious diseases, which led to innumerable victims. The rationale and the subsequent development of measures for the prevention and control of epidemics were an urgent necessity in the process of human evolution. In modern conditions, epidemiology acquires a fundamentally different quality, allowing it to approach the exact sciences, through the introduction of new research methods. There are serious achievements of this discipline in reducing infectious diseases.
Infectious diseases for many years occupy the first place. And if so, the doctor – a specialist of the sanitary and epidemiological service should fully know the system of measures for antiepidemic care of the population and practically master the methodology and conduct of basic measures to reduce the infectious morbidity.
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