The epidemic process. Characteristics of the epidemic process

The infectious and epidemic process is a continuous type interaction at the population and species levels. It involves inhomogeneous evolutionary-conjugate signs of the relationship between each other, the parasite causative agent and the human body. The infectious and epidemic process manifests itself as asymptomatic and manifest forms. They are distributed among the population by groups at risk of infection or disease, time and territory.

Historical background

Such a concept as an "epidemic process" began to be used from the beginning of the 19th century. One of the early ideas about this phenomenon was formulated by Ozanam in 1835. Then a whole series of scientists began to develop the idea. The very term "epidemic process" was introduced by Gromashevsky in 1941. Further, Belyakov specified the content of the definition. Later, he also put forward a provision on self-regulation in the epidemic process.

Sections

Of only three. Distinguish 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 the information in this section makes it possible, in general formulations, to answer the question of what are the bases of epidemiology. In clinical medicine - in an area where pathological conditions are studied at the organism level - a similar section is called "etiology". The second link reflects the course of the formation of the phenomenon. This section answers the question of how it begins. In clinical medicine, a similar sphere is called "pathogenesis." The third section reveals the manifestations that accompany the epidemic process; Information that reflects the signs of the phenomenon is systematized. In clinical medicine, a similar section is called semiotics. Next, consider the categories in more detail.

Conditions and causes

The interaction of the pathogen and the human body proceeds continuously and continuously in space and time. There are various factors in the epidemic process. They include, for example, biological. These factors of the epidemic process form the reasons for the pathological interaction. There is also a second category. Natural and social factors ensure the regulation of the conditions under which the process takes place. Interaction is possible only if there is a cause and conditions.

Driving forces of a biological nature

This factor is a parasitic system in which a certain interaction takes place. Its sides are characterized by some distinctive features. So, parasites show pathogenicity, the host is receptivity.

Social forces

These factors include a set of social conditions that contribute to or impede the course of the epidemic process. Among them are:

• Sanitary provision of settlements.
• Activity of inhabitants.
• Social development.

Population activity

It indirectly and directly affects the intensity of the course of the epidemic process. The stronger the social activity, the more pronounced the interaction of parasites and the body. Historically, the peak comes from revolutionary and military periods. The activity of the population can be manifested at the level of the whole society or a particular family.

Sanitary improvement

Its level directly affects the intensity with which the epidemic process is taking place. The concept of sanitary improvement includes the frequency of collection and disposal of food and solid waste. Also, the state of drainage and water supply systems is included.

Social Progress

The level of industrial and social development has an indirect effect on the conditions in which the epidemic process takes place. In this case, it can have both positive and negative effects. Examples of the former can be considered improved nutrition and quality of life of the population and, as a result, increased immunity of residents, as well as changes in the culture of behavior, hygienic education, technological progress. Negative influence 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

These factors include abiotic and biotic components. The latter are elements of living nature. As an example of the regulatory impact of biotic components, one can cite a change in the intensity of the course of the epidemic process against the background of a different number of rodents in natural-focal type infections. In vector-borne zoonoses, migration and the number of arthropods have a regulating effect on the severity of the phenomenon. 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 Gromashevsky defines the course of interaction of the parasite and the human body along the triad. So, there are the following links of the epidemic process:

• Source of the pathogen.
• Transmission mechanism.
• Susceptible organism.

The last links of the epidemic process have their own classification.

Source of pathogen

It is an infected human, animal or plant organism. From it, infection of susceptible people can occur. A complex of sources forms a reservoir. For anthroponoses, the person who exhibits an asymptomatic or manifest pathology is the causative agent, animals (wild, synanthropic, or domestic) are for zoonoses. And for sapronoses it will be abiotic elements of the environment.

Transmission of pathogens

Epidemiology of the disease involves a certain way of moving parasites into a healthy body from the affected. According to the second law Gromashevsky, the transmission of the pathogen occurs depending on its main localization. It can be blood, skin scales, mucus, feces. As a path of movement, there is a sequence and a set of transmission factors by means of which the mechanism itself is realized.

Ways of penetration of parasites

1. Aerosol path. It includes the following methods:

- airborne (this is transmitted to ARVI, meningococcal infection);

- air-dust (along this path are pathogens of tuberculosis, scarlet fever).

2. Fecal-oral route. To it carry such ways, as:

- contact-household;

- water;

- food.

3. Contact path. It includes direct and indirect methods of transmission.

4. The transmissive pathway. This category includes such methods as:

- artificial (related to medical manipulations: associated with surgery, injectable, transplant, transfusion, due to diagnostic procedures);

- natural (with a contamination type the pathogen is excreted with excreta of the transporter, with inoculation type it is injected with saliva).

Additional classification

There are several transmission factors. In particular, they distinguish the final, intermediate and initial. Transmission factors are also conventionally divided into additional and basic ones. The phases of parasite movement include:

• Isolation from the carrier organism.
• Stay in the external environment.
• Penetration into the organism predisposed to pathology.

Susceptibility

It is the ability of the host to become infected with pathologies provoked by parasites. This manifests itself in the form of pathological and response protective specific (immune system) and nonspecific (stability) reactions. There are the following types of susceptibility:

• Individual (phenotypic and genotypic).
• Species.

Immunity acts as a specific response to the penetration of a foreign agent. Stability (resistance) is a complex of protective reactions of a nonspecific type.

Characteristics of the epidemic process

The interaction of the parasite and man is manifested in the form of infection of the latter. Subsequently, the susceptible host may become ill or become carriers of the pathogen. At the population-specific level, manifestations are presented in the form of sporadic morbidity, the presence of an epidemic (epiphytotic, epizootic) or natural focus, outbreak, epidemic or pandemic.

Intensity

Sporadic distribution is peculiar to a certain collective, 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 temporal and territorial parameters. An epidemic outbreak is a short-term increase in the incidence of disease within a specific team. It lasts for one or two incubation periods. The epidemic is an increase in the incidence rate to the region or region. As a rule, it covers one season per year. A pandemic characterizes the level of infection that lasts for several years or decades. The pathology in this case spreads to the continents.

Unevenness of manifestation

It can relate to territories, time, population groups. In the first case, the classification is based on the zone of distribution of the reservoir. In particular, they distinguish:

• Global area. In this case, the interaction is between the person and the reservoir of anthroponoses.
• The regional area is a natural focal zoonotic.

Uneven time:

• Cyclicity.
• Seasonality.
• Irregularity of infection rises.

Unevenness by population groups is classified by epidemically significant and formal characteristics. The latter include the following groups:

• Age.
• Professional.
• Depending on the place of residence (urban or rural).
• Unorganized and organized.

Distribution according to epidemically significant signs is carried out on the basis of logical conclusions of specialists. It can include various factors, such as, for example, vaccination.

Socio-ecological concept

It is based on the positions of the systems approach. Through this tool, the concept reveals the hierarchical structure of the process. It also reveals the functional interaction between the phenomena inherent in 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 spread of parasitic forms of microorganisms among people. In the structure were allocated 2 levels: eco-and sotsecosystem.

Parasitic system

It is discrete. This means that it includes individuals in the host population. In the body, the infectious process progresses, expressed in the form of carriage or expressed clinically pathologies. When implementing one or another way of transmission, the interaction of the pathogen and the susceptible organism is transformed into an interpopulation one. In this regard, the parasitic system contains a hierarchy of many infectious processes. The concept of the epidemic process becomes abstract without understanding the meaning of the transmission mechanism.

Hierarchical structure

It has a multi-level character and includes several subordinate layers:

• Organism . Speech in this case goes directly about the infectious process. In it, the interacting systems are represented 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 the cells of the target organism.
• Tissue-organ. At this level, the local subset of the parasite interacts with the specific organization of certain tissues and host organs.
• Subcellular (molecular). Here, genetic apparatuses interact with biological molecules of parasites and hosts.

The highest in the structure of the epidemic process is the sotsecosystemic level, in which the ecosystem is included as one of the internal subcategories. The second is represented as a social organization of society. As the reason for the emergence and further development of the epidemic process is precisely the interaction of these two subsystems. In this case, the phenomena in the environmental structure are regulated by the social unit.

Example

In February 2014 in Guinea (West Africa) Ebola epidemic began. It continues to this day. At the same time Ebola epidemic went beyond the state and spread to other countries. The infection zone included, in particular, Sierra Leone, Liberia, the United States, Senegal, Mali, Spain, Nigeria. This case is unique, as the disease began for the first time in West Africa. Doctors in countries where pathology has spread, do not have the experience of fighting it. The situation is aggravated by the probability of panic among the population due to disinformation. To help the Guinean government, funds and personnel were sent to various international and national organizations. In particular, assistance was rendered by: the Center for Epidemiology of the United States, Russia, Rospotrebnadzor, the European Commission. Assistance was sent to the Economic Community of Western Europe. On the territory of Guinea, there was a laboratory for epidemiology. Experts collected and analyzed information about the disease. The epidemiology center provided support to the population, isolated the infected from the healthy inhabitants. As noted by WHO Director General Keiji Fukuda, the outbreak has become the strongest of all in practice.