Инфекционный и эпидемический процесс представляют an interaction of continuous type at the population and species levels. The pathogen-parasite pathogen and the human organism, which are heterogeneous in terms of evolutionary conjugate characteristics, take part in it. Infectious and epidemic processes manifest asymptomatic and manifest forms. They are distributed among the population at risk of infection or disease, time and territory.
Historical background
Such a thing as an "epidemic process"Began to be used since the beginning of the 19th century. One of the earliest ideas about this phenomenon was formulated by Ozanam in 1835. Further, a number of scientists engaged in the development of ideas. The term "epidemic process" was introduced by Gromashevsky in 1941. Then Belyakov clarified the content of the definition. Later, he also put forward a provision on self-regulation in the epidemic process.
Sections
Of all three. There are the following sections of the epidemic process:
- Conditions and reason.
- The mechanism of the epidemic process.
- Manifestations.
The first section reveals the essence of the process.It reflects the internal causes of the formation and the conditions under which it proceeds. The systematization of information in this section makes it possible, in general terms, to answer the question of what are the foundations of epidemiology. In clinical medicine - in the area where the study of pathological conditions is carried out at the organism level, a similar section is called "etiology". The second link reflects the course of formation of the phenomenon. This section answers the question of how it begins. In clinical medicine, a similar field is called pathogenesis.
Conditions and reasons
The interaction of the pathogen and the human bodyflows in space and time continuously. There are various factors of the epidemic process. These include, for example, biological. These factors of the epidemic process form the reasons why the pathological interaction begins. There is also a second category. Natural and social factors provide regulation of the conditions under which the process takes place. Interaction is possible only if there are reasons and conditions.
Biological Drivers
This factor is a parasitic system in whichthere is a certain interaction. Some distinctive features are characteristic of its sides. So, parasites show pathogenicity, the owner - susceptibility.
Social forces
These factors include a complex of social conditions that contribute to or impede the course of the epidemic process. Among them are:
- Sanitary provision of settlements.
- Active residents.
- Social development.
Population activity
It indirectly and directly affectson the intensity of the flow of the epidemic process. The stronger the social activity, the more pronounced the interaction of the parasites and the organism. Historically, the peak falls on the revolutionary and war periods. Population activity can occur at the level of the whole society or a specific family.
Sanitary improvement
Its level directly affectsthe intensity with which the epidemic process. The concept of sanitary improvement includes the frequency of collection and disposal of food and solid waste. It also refers to the state of water disposal systems and water supply.
Social Progress
The level of production and publicdevelopment has an indirect effect on the conditions in which the epidemic process. However, it can have both positive and negative effects. Examples of the first include the improvement of nutrition and the quality of life of the population and, as a result, an increase in the immunity of residents, as well as changes in behavioral culture, hygienic education, and technological progress. The negative impact is manifested in an increase in the number of drug addicts and alcoholics, changes in sexual culture (spread of viral hepatitis, HIV infection), deterioration of environmental conditions, weakening of the body's defenses.
Natural conditions
К этим факторам относят абиотические и biotic components. The latter are elements of nature. As an example of the regulatory effect of biotic components, we can cite a change in the intensity of the course of the epidemic process against the background of different numbers of rodents in natural-focal type infections. In transmissible zoonoses, migration and the number of arthropods have a regulating effect on the severity of the phenomenon. The abiotic components include landscape geographical conditions and climate. For example, when approaching the equator, the variety of nosological forms of pathologies increases.
Epidemiology of Infectious Diseases
The first law of Gromashevsky determines the course of the interaction of the parasite and the human body according to the triad. So, there are the following links of the epidemic process:
- The source of the pathogen.
- The transmission mechanism.
- Susceptible organism.
The last links of the epidemic process have their own classification.
Source of pathogen
He is an infected human,animal or plant organism. It can result in infection of susceptible people. A complex of sources forms a reservoir. For anthroponosis, the causative agent is a person who has an asymptomatic or manifest form of pathology, for zoonoses animals (wild, synanthropic, or domestic). And for sapronoses, these will be abiotic elements of the environment.
Pathogen transmission
The epidemiology of the disease suggestsa certain way to move the parasites into a healthy organism from the affected. According to the second law of Gromashevsky, the transmission of the pathogen occurs depending on its main localization. This may be blood, skin scales, mucus, feces. The sequence and the combination of transfer factors, with the help of which the mechanism itself is realized, act as a path of movement.
Parasite penetration methods
1. Aerosol path. It includes the following methods:
- airborne (as transmitted by ARVI, meningococcal infection);
- airborne dust (pathogens of scarlet fever go along this path).
2. Fecal-oral method. It includes such ways as:
- contact and household;
- water;
- food.
3. Contact path. It includes direct and indirect modes of transmission.
4. The transmissible path. This category includes such methods as:
- artificial (associated with medical procedures: associated with surgery, injection, transplantation, transfusion, due to diagnostic procedures);
- natural (in case of a contamination type, the pathogen is secreted with carrier excrement, in case of inoculation it is injected with saliva).
Additional classification
Существует несколько факторов передачи.In particular, allocate the final, intermediate and initial. Transmission factors are also conditionally divided into additional and major ones. The phases of movement of the parasite include:
- Excretion from the body-carrier.
- Stay in the environment.
- Penetration into a predisposed organism.
Susceptibility
It represents the master's abilityto become infected with pathologies provoked by parasites. This is manifested in the form of pathological and protective response specific (immune system) and non-specific (resistance) reactions. The following types of susceptibility are distinguished:
- Individual (pheno-and genotypic).
- Species.
Immunity acts as a specific response to the penetration of a foreign agent. Resistance (resistance) is a complex of non-specific type of defense reactions.
Characteristics of the epidemic process
The interaction of the parasite and man is manifested inas an infection of the latter. Subsequently, the susceptible host may become ill or become a carrier of the pathogen. At the population-species level, manifestations are presented in the form of sporadic morbidity, the presence of an epidemic (epiphytotic, epizootic) or natural focus, an outbreak, an epidemic, or a pandemic.
Intensity
Sporadic distribution is commona specific team, season, territory. Epidemic morbidity is a temporary increase in the level of infection. The subsequent classification in this case is carried out in accordance with the time and territorial parameters. An epidemic outbreak is a short-term increase in incidence within a specific team. It continues during one or two incubation periods. An epidemic is an increase in incidence to a region or region. It usually covers one season per year. A pandemic characterizes the level of infection that lasts for several years or decades. Pathology in this case extends to the continents.
Uneven manifestation
It can concern territories, time, groups of the population. In the first case, the classification is based on the zone of distribution of the reservoir. In particular, emit:
- Global area. In this case, the interaction takes place between the person and the reservoir of anthroponoses.
- Regional area - This is a natural focal zoonosis.
Unevenness in time:
- Cyclicity.
- Seasonality.
- Irregularity rises of infection.
Non-uniformity by population groups is classified according to epidemically significant and formal signs. The latter include groups:
- Age.
- Professional.
- Depending on the place of residence (urban or rural area).
- Unorganized and organized.
Distribution in accordance with epidemically significant signs is carried out on the basis of logical conclusions of specialists. It may include various factors, such as, for example, immunization.
Socio-ecological concept
It is based on the positions of the system approach.Through this tool, the concept reveals the hierarchical structure of the process. It also reveals the functional interaction between the phenomena peculiar to each level. In accordance with the concept, the epidemic process is presented in the form of a complex multi-stage system. It ensures the existence, reproduction and distribution of parasitic forms of microorganisms among people. The structure was divided into 2 levels: eco-and social ecosystem.
Parasitic system
It is discrete.This means that it consists of individuals in the host population. In the body progresses an infectious process, expressed in the form of carriage or expressed clinically pathologies. When implementing a particular pathway of transmission, the interaction of the pathogen and the susceptible organism turns into an interpopulation. In this regard, the parasitic system contains a hierarchy of many infectious processes. The concept of an epidemic process becomes abstract without an understanding of the meaning of the transmission mechanism.
Hierarchical structure
It has a multi-level character and includes several co-ordinated layers:
- Organizational. Speech in this case is directly aboutinfectious process. In it, the interacting systems are presented in the form of an organism subpopulation of the pathogen and the organization of the biological balance of the macroorganism.
- Cellular. At this level there is a system consisting of a separate individual of the parasite and a cell of the target organism.
- Tissue-organ. At this level, the local subpopulation of the parasite interacts with the specific organization of certain tissues and organs of the host.
- Subcellular (molecular). Here, genetic devices interact with biological molecules of the parasites and the host.
Higher in the structure of the epidemic processIt is considered the social-ecosystem level, in which the ecosystem is included as one of the internal subcategories. The second is presented in the form of social organization of society. The reason for the emergence and further development of the epidemic process is precisely the interaction of these two subsystems. At the same time, phenomena in the ecostructure are regulated by means of a social unit.
Example
In February 2014 in Guinea (West Africa)Ebola epidemic began. It continues to this day. At the same time, the Ebola epidemic went beyond the borders of the state and spread to other countries. The zone of infection included, in particular, Sierra Leone, Liberia, USA, Senegal, Mali, Spain, Nigeria. This case is unique because the disease began for the first time in West Africa. Doctors in countries where pathology has spread have no experience in dealing with it. The situation is exacerbated by the likelihood of panic among the population due to misinformation. Funds and personnel were sent by various international and national organizations to help the Guinean government. In particular, assistance was provided by: the Center for Epidemiology of the United States, Russia, Rospotrebnadzor, the European Commission. Help sent and the Economic Community of Western European States. There was an epidemiology laboratory in Guinea. Experts collected and analyzed information about the disease. The Center for Epidemiology provided support to the population, isolated those infected from healthy residents. As WHO Director-General Keiji Fukuda noted, the outbreak was the strongest of all in practice.
