The infectious and epidemic process is a continuous type of interaction at the population and species levels. It involves the pathogen-parasite and the human body that are heterogeneous in terms of evolutionary-related signs of relations to each other. Infectious and epidemic process are manifested by asymptomatic and manifest forms. They are distributed among the population according to risk groups for infection or disease, time and territory.
Historical information
Such a concept as an "epidemic process" began to be used from 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 took up the development of the idea. The term "epidemic process" itself was introduced by Gromashevsky in 1941. Further, Belyakov clarified the content of the definition. Later they also put forwardposition on self-regulation in the epidemic process.
Sections
Out of only three. There are the following sections of the epidemic process:
- Conditions and reason.
- The mechanism for the development of the epidemic process.
- Manifestations.
The first section reveals the essence of the process. It reflects the internal causes of formation and the conditions under which it proceeds. The systematization of the 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 field where the study of pathological conditions is carried out at the organismal 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 starts. In clinical medicine, a similar area is called "pathogenesis".
The third section reveals the manifestations that accompany the epidemic process; information reflecting the signs of the phenomenon is systematized. In clinical medicine, a similar section is called semiotics. Next, let's look at the categories in more detail.
Conditions and Causes
The interaction of the pathogen and the human body proceeds continuously in space and time. 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 secondcategory. Natural and social factors provide regulation of the conditions under which the process takes place. Interaction is possible only if there is a cause and conditions.
Biological driving forces
This factor is a parasitic system in which a certain interaction takes place. Its sides have some distinctive features. So, parasites show pathogenicity, the host shows susceptibility.
Social Forces
These factors include a set of social conditions that contribute to or hinder the course of the epidemic process. Among them are:
- Sanitary provision of settlements.
- Activity of residents.
- Social development.
Activity of the population
It indirectly and directly affects the intensity of the course of the epidemic process. The stronger the social activity, the more pronounced the interaction between the parasites and the organism. Historically, the peak falls on the revolutionary and military periods. The activity of the population can manifest itself at the level of the whole society or a particular family.
Sanitation
Its level directly affects the intensity with which the epidemic process proceeds. The concept of sanitation includes the frequency of collection and disposal of food and solid waste. It also includes the state of water disposal and water supply systems.
Social Progress
The level of production and social development has an indirect influence on the conditions in whichepidemic process. However, it can have both positive and negative impacts. Examples of the former include improving the nutrition and quality of life of the population and, as a result, increasing the immunity of residents, as well as changes in the culture of behavior, hygiene education, and technological progress. The negative impact is manifested in an increase in the number of drug addicts and alcoholics, changes in sexual culture (the 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 wildlife. As an example of the regulatory effect 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 infections of the natural focal type. In transmissible zoonoses, migration and the number of arthropods have a regulatory effect on the severity of the phenomenon. The abiotic components include landscape geographic conditions and climate. For example, when approaching the equator, the variety of nosological forms of pathologies increases.
Epidemiology of infectious diseases
Gromashevsky's first law determines the course of interaction between the parasite and the human body according to the triad. So, there are the following links of the epidemic process:
- Exciter source.
- Transmission mechanism.
- Susceptible organism.
Last linksepidemic process have their own classification.
Exciter source
It is an infected human, animal or plant organism. It can infect susceptible people. The complex of sources forms a reservoir. For anthroponoses, 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.
Exciter transfer
The epidemiology of the disease involves a certain way of moving parasites into a he althy organism from the affected one. According to the second law of Gromashevsky, the transmission of the pathogen occurs depending on its main localization. It can be blood, skin scales, mucus, feces. The sequence and set of transmission factors, with the help of which the mechanism itself is implemented, acts as a path of movement.
Methods of parasite penetration
1. Aerosol way. It includes the following ways:
- airborne (this is how ARVI, meningococcal infection is transmitted);
- air-dust (causative agents of tuberculosis, scarlet fever pass along this path).
2. The fecal-oral route. It includes paths such as:
- contact household;
- water;
- food.
3. contact path. It includes direct and indirect modes of transmission.
4. transmission path. To thiscategories include ways such as:
- artificial (associated with medical manipulations: associated with surgery, injection, transplantation, transfusion, due to diagnostic procedures);
- natural (with the contamination type, the pathogen is excreted with the excrement of the carrier, with the inoculation type it is injected with saliva).
Additional classification
There are several transmission factors. In particular, there are final, intermediate and initial. Transmission factors are conditionally also divided into additional and main ones. The phases of parasite movement include:
- Isolation from a carrier.
- Staying outside.
- Penetration into an organism predisposed to pathology.
Susceptibility
It represents 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 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. Stability (resistance) is a complex of protective reactions of a non-specific type.
Characteristics of the epidemic process
The interaction between a parasite and a human is manifested in the form of infection of the latter. Subsequently, a susceptible host mayget sick 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, outbreak, epidemic or pandemic.
Intensity
Sporadic distribution is characteristic of a certain team, season, territory. Epidemic incidence is a temporary increase in the level of infection. Subsequent classification in this case is carried out in accordance with temporal and territorial parameters. An epidemic outbreak is a short-term increase in morbidity within a particular community. It continues for one or two incubation periods. An epidemic is an increase in the level of disease to an area or region. As a rule, it covers one season per year. A pandemic characterizes the level of infection lasting for several years or decades. In this case, the pathology spreads to the continents.
Irregular appearance
It can refer to territories, time, population groups. In the first case, the classification is based on the distribution zone of the reservoir. In particular, allocate:
- Global range. In this case, the interaction is carried out between a person and a reservoir of anthroponoses.
- The regional range is natural focal zoonoses.
Irregularity in time:
- Cyclic.
- Seasonal.
- Irregularityrises in infection.
Unevenness across population groups is classified according to epidemiologically significant and formal features. The latter include groups:
- Age.
- Professional.
- Depending on where you live (urban or rural).
- Disorganized and organized.
Distribution in accordance with epidemically significant signs is carried out on the basis of the logical conclusions of specialists. It may include various factors, such as vaccination.
Socio-ecological concept
It is based on the positions of a systematic 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. According to 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. The structure was divided into 2 levels: eco- and social-ecosystem.
Parasitic system
She is discrete. This means that it consists of individual individuals in the host population. An infectious process progresses in the body, expressed in the form of carriage or clinically expressed pathologies. With the implementation of one or another route of transmission, the interaction of the pathogen and the susceptible organism turns 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 multilevel character and includes several subordinate layers:
- Organismal. In this case, we are talking directly about the infectious process. In it, the interacting systems are presented in the form of an organismal subpopulation of the pathogen and the organization of the biological balance of the macroorganism.
- Cellular. At this level, there is a system consisting of an individual 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 host tissues and organs.
- Subcellular (molecular). Here, the genetic machinery interacts with the biological molecules of the parasites and the host.
The highest in the structure of the epidemic process is the social-ecosystem level, which includes the ecosystem as one of the internal subcategories. The second is presented in the form of the social organization of society. It is the interaction of these two subsystems that acts as the reason for the emergence and further development of the epidemic process. At the same time, the phenomena in the eco-structure are regulated through the social subdivision.
Example
In February 2014, an Ebola epidemic broke out in Guinea, West Africa. It continues to this day. At the same time, the Ebola epidemic went beyond the borders of the state andspread to other countries. The infection zone included, in particular, Sierra Leone, Liberia, the United States, Senegal, Mali, Spain, and Nigeria. This case is unique because the disease first appeared in West Africa. Doctors in countries where the pathology has spread do not have 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 to assist the Guinean Government by various international and national organizations. In particular, assistance was provided by: Center for Epidemiology of the USA, Russia, Rospotrebnadzor, European Commission. Assistance was also sent by the Economic Community of Western European States. An epidemiology laboratory worked on the territory of Guinea. Specialists collected and analyzed information about the disease. The Center for Epidemiology provided support to the population, isolated the infected from he althy residents. As noted by WHO Director General Keiji Fukuda, the outbreak was the strongest of all in practice.
