Its biological basis is the interaction three constituent links("triad Gromashevsky" ):
1) the source of the infectious agent,
2) pathogen transmission mechanism
3) a susceptible organism (collective).
Source of infection - it is a living infected organism, which is the natural environment for the existence of the pathogen, where it multiplies, accumulates and is released into the external environment.
Pathogen transmission mechanism- this is an evolutionarily established natural way of moving the pathogen from the source of infection to a susceptible human or animal organism. (aspiration, fecal-oral, contact, transmissible, vertical,artificial (artificial).
Susceptible organism (collective). Susceptibility - a species property of a human or animal body to respond with an infectious process to the introduction of a pathogen. The state of susceptibility depends on a large number of factors that determine both the state of the macroorganism and the virulence and dose of the pathogen.
The possibility of occurrence and spread of morbidity among the population depends on 3 factors: biological, natural and social.
natural factor- these are climatic and landscape conditions that contribute to or hinder the development of the epidemic process.
14. The doctrine of the epidemic process. The source of infection as a necessary prerequisite for the emergence and maintenance of the continuity of the epidemic process. Characterization of sources of infection. reservoir of infection.
infectious process- the interaction of the pathogen and a susceptible organism (human or animal), manifested by the disease or carriage of the infectious agent.
Source of infection is a living infected organism, which is the natural environment for the existence of the pathogen, where it multiplies, accumulates and is released into the external environment.
reservoir of infection a set of biotic (human or animal organism) and abiotic (water, soil) objects that are the natural habitat of the pathogen and ensure its existence in nature. Those. this is the habitat without which the pathogen cannot exist as a biological species.
There are the following sources
Gromashevsky who was the first to develop in detail the basic laws of epidemiology, the theory of the mechanism of infection transmission and the driving forces of the epidemic process. section - The mechanism of development of the epidemic process: the mechanism of transmission L. The elementary basis of the epidemic process is: The source of the pathogen of infection The mechanism of transmission of pathogens The susceptibility of the population. human animal abiotic environment Category I source of infection - human Patient Infectious carrier Form of the disease:...
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F KSMU 4/3-04/01
IP No. 6 UMS at KazGMA
KARAGANDA STATE MEDICAL UNIVERSITY
Department of Epidemiology and Communal Hygiene
LECTURE
Topic: " The concept of the epidemic process».
Subject: BDO 26 Epid - 3226 Epidemiology
Specialty: 051301 - " General Medicine »
Course 3
Time (duration) 1 hour
Karaganda 2010
Approved at the meeting of the department
"____" ____________ 2010 Protocol No. ___
Head Department of Epidemiology and
of Communal Hygiene Doctor of Medical Sciences, Professor __________ Shabdarbayeva M.S.
Topic: The concept of the epidemic process.
- Purpose: mastering the theoretical, methodological and organizational foundations of epidemiology.
- Lecture plan:
- Lecture abstracts:
The main sections of the doctrine of the epidemic process
Various aspects of the theory of "epidemics" and "epidemic process" are reflected in the fundamental works of D.K. Zabolotny, L.V. Gromashevsky, B.A. Bashenina, M.N. Solovieva, N.A. Semashko, E.N. Pavlovsky, V.N. Beklemesheva, I.I. Elkina, B.M. Zhdanova and others, in particular D.K. Zabolotny, V.A. Bashenin.
The founder of the doctrine of the epidemic process should be considered L.V. Gromashevsky, who was the first to develop in detail the basic laws of epidemiology, the theory of the mechanism of infection transmission and the driving forces of the epidemic process.
There are several definitions of the epidemic process:
2. I.I. Elkin (1962) – An epidemic process is a series of epidemic foci that are interconnected and arise from one another.
This definition is also based on the external manifestation of infectious diseases in human society. This notion of the epidemic process is unfortunate, because in the definition it is impossible to introduce the concept of "epidemic focus", which requires additional clarification.
The first part of the definition: the interaction of the pathogen and the host organism at the population level - the essence, nature of the epidemic process; the final part of the definition: manifested by manifest and asymptomatic forms of infections in humans - a manifestation of the epidemic process; the middle part of the definition is the conditions necessary for the action of the cause.
Thus, the modern definition of the epidemic process:
Consideration of any process or phenomenon must be carried out in three aspects: why the process develops, i.e. its cause: how the process develops, i.e. how the cause functions and what conditions and how they affect it; how this process (phenomenon) manifests itself. In this regard, 3 interrelated sections of the doctrine of the epidemic process are distinguished (Table 1):
Section 1 - Factors of the epidemic process:
- biological
- social
- natural
Section 2 - The mechanism of development of the epidemic process:
Section 3 - Manifestation of the epidemic process:
- by level
- by territory
- by time
- by groups
Factors of the epidemic process are biological, social, natural. Their influence on the development of the epidemic process.
The pathogen and host populations are heterogeneous and dynamically variable. They consist of individuals with genetic and phenotypic differences.
The heterogeneity of the pathogen population is manifested in the differences in individuals in terms of virulence, toxigenicity, resistance to environmental factors, including disinfectants, drug resistance, enzymatic activity, sensitivity to phages, etc. and in conjunction with the dose of the pathogen and the degree of susceptibility of the organism of the host population determine the variety of forms of manifestation of the infectious process, the effectiveness and differentiation in the approach of carrying out activities in specific epidemiological approaches.
The accelerating pace of anthropogenic transformation of the biosphere as a result of scientific and technological progress at the present stage is a powerful factor influencing the evolution of infectious diseases. Such intensive processes in the modern world as pollution of the environment with industrial waste, the widespread use of pesticides, biological products, urbanization, the intensification of population migration, the massive development of tourism and vehicles, international trade in products, raw materials, centralization of water supply and nutrition, sanitary and communal improvement of the population places, population size and density, birth rate, health status, etc. All these regulatory mechanisms act on
biological subsystem and lead to the activation or inhibition of the epidemic process, as well as significant changes in the structure of ecosystems, a change in the epidemic process of previously unknown pathogens, a change in the properties of known agents, a change in the reactivity and susceptibility of a person, which leads to an acceleration of the evolution of infectious diseases.
Natural conditions primarily affect diseases, the source or live carrier of which pathogens are animals. Features of the annual biological cycle observed in animals, significantly affect the activity of the epizootic and indirectly on the epidemic process; with transmissible anthroponoses, this influence is expressed directly.
The elementary cell of the epidemic process.
The elementary basis of the epidemic process is:
- Source of the infectious agent
- Mechanism of transmission of pathogens
- The susceptibility of the population.
However, the study of these individual links does not allow us to fully understand its nature, essence.
I link
The source of infection is the natural habitat of the pathogen, where it lives, reproduces, feeds and is released into the environment.
|
Sick |
Infectious carrier |
|
Form of the disease: - manifest Acute Erased Acute chronic Chronic abortive |
there are no clinical symptoms a) convalescents b) immune c) transitory |
|
People are practically healthy, but they excrete the pathogen |
|
|
incubation, prodrome, peak of illness, convalescence |
|
|
According to the severity of the disease |
1st link
The transmission mechanism is implemented through 3 phases (stages):
1. removal of the pathogen into the external environment from the infected organism.
The first stage of the transmission mechanism is carried out in the process:
Physiological reactions: defecation, urination, respiration,
Talk
From pathological intensification: diarrhea
With pathological acts accompanying the disease: coughing, sneezing, vomiting, ulcers, erosion on the skin and mucous membranes.
2. temporary stay in the external environment
In abiotic (air, soil, household items, dirty hands) and biotic (insects) environmental objects. In this phase of the transmission mechanism, not only the preservation of the pathogen is ensured, but also their delivery to a new organism is realized.
3. introduction of the pathogen into a new susceptible organism:
By inhalation of contaminated air;
By drinking contaminated water and food;
Through contact (contact with contaminated objects) with objects;
Through the bites of blood-sucking insects.
Methods for removing the pathogen from the infected organism (stage 1 of the transmission mechanism) and introduction into the susceptible organism (stage 3 of the transmission mechanism) are determined by its specific localization in the host organism.
In turn, this localization determines the mechanism of transmission of the pathogen from an infected organism to a susceptible one. This is the principle of mutually conditioned correspondence between the localization of the pathogen in the host organism and the mechanism of its transmission from one host to another.
On the basis of the main localization of the pathogen in the human body, L.V. Gromashevsky singled out 4 transmission mechanisms:
I. - a erosolic (a erogenous, respiratory, a spiratory)
The causative agent is localized in s wicked ways.
ІІ . Fecal-oral.
The specific localization of the pathogen is in the intestine.
ІІІ . Transmissible.
The specific localization of the pathogen is in the circulatory system.
I V . Contact.
Specific localization of the pathogen - on the skin, mucous membranes,
The 2nd and 3rd phases of the transmission mechanism are realized through transmission factors - these are the elements of the external environment (abiotic and biotic) that ensure the transfer of the pathogen from one organism to another
|
Transfer mechanism |
Transmission factors |
Transmission routes |
|
1. aerosol |
air dust |
Airborne |
|
2. Fecal-oral |
food, water, soil, household items, flies |
food, water, contact household |
Transmission factors can be: (for fecal-oral transmission mechanism)
a) primary - those on which the pathogen enters during the implementation of stage 1 of the transmission mechanism
b) final - deliver the pathogen to the infected organism
c) intermediate - deliver the pathogen from the primary factors of transmission to the final
Scheme
Food
Arms
Feces soil mouth
Water
Food
Transmission factors can be living arthropods, they are called carriers of pathogens.
Distinguish:
A) mechanical carriers (non-specific), (fly) - mechanical transmission of pathogens on the legs.
B) blood-sucking carriers (specific) flea, mosquito, louse, ticks, etc. - pathogens multiply in their body or go through a development cycle.
Transmission routes - these are specific elements of the external environment or a combination of them, which ensure the transfer of the pathogen from one organism to another. See diagram.
The transmission path is designated by the final transmission factor.
With the development of the doctrine of the epidemic process, there was a refinement of certain provisions of the theory of the mechanism of transmission of pathogens. In particular, in addition to the four main mechanisms of transmission of pathogens, their localization in germinal (sex) cells was revealed and, accordingly, the 5th type of transmission mechanism was identified - the vertical transmission mechanism - from mother to fetus, i.e. directly from one generation to another (eg HIV infection, toxoplasmosis, rubella).
The above variants of the transmission mechanism were formed in natural conditions in accordance with the localization of pathogens in the body. In practical work, unusual "artificial" and artificial methods of transmission or methods of infection are possible. For example, in laboratories and in the production of viral preparations in case of violation of safety regulations, technological process, in case of accidents.
Unusual ways of infection (methods of transmission) are possible during medical manipulations - injections, blood transfusions, endoscopy, organ transplants, surgical, dental, gynecological interventions (parenteral method of transmission of infection.
The theory of natural foci of infectious diseases
Founder E.N. Pavlovsky. The essence of the theory is that it explains the development of diseases by the ingestion of pathogens that exist due to circulation among wild animals into the human body. As a rule, polypathogenic pathogens circulate among wild animals (i.e., they cause disease in several animal species) and a person, once in the environment of the natural circulation of the pathogen, becomes ill.
natural hearth - a section of the territory of the geographical landscape within which among wild animals the pathogen is transmitted from the donor to the recipient.
natural hearth - a pathogen population that has formed independently of human activity, together with populations of vertebrate hosts that support its existence, populations of blood-sucking arthropods (with transmissible infections) and specific environmental conditions (with sapronoses).
Anthropurgic focuszoonotic infection - a focus formed in connection with human economic activity.
Human infection occurs in connection with epizootic (natural, anthropurgic) foci and, as a rule, without subsequent transmission of the pathogen from person to person.
Man is a biological dead end for pathogens of the zoonoses group.
Only in some cases is a chain of infections observed similar to how it occurs with anthroponotic infections (pneumonic plague).
Infection of a susceptible person is associated with his stay without special protection in the territory of a natural focus only at the time when he is in a valence state, i.e. the period of epidemiological activity of infected host animals and arthropod vectors.
Agricultural (domesticated) animals and synanthropic rodents can serve as a link in the transition of some natural focal infections from the wild to humans.
These infections primarily include rabies, leptospirosis, toxoplasmosis, eryzepeloid, listerellosis, and possibly brucellosis.
- Literature:
1. Amireev S.A. Epidemiology Textbook - Almaty. - 2002. - 2 volume. - 693s.
2. Pokrovsky V.I., Pak S.G., Briko N.I. etc. Infectious diseases and epidemiology. Textbook for medical schools. 2nd edition. - M. - GEOTAR - MED, 2003. - 816s.
3. Cherkassky B.L. Guide to General Epidemiology. – M.: Medicine. - 2001. - 435p.
4. Belyakov V.D., Yafaev R.Kh. Epidemiology. M., 1989, 416s.
5. Belozerov E.S., Ioannidi E.A. Course of epidemiology: Proc. Pos. For to lay down. and ped. fak. medical universities // Elista: Dzhangar, 2005. - 136p.
6. Epidemiology; Tutorial / N.D. Yushchuk, M.A. Zhogova, V.V. Bushueva and others - M.: Medicine, 1993. - 336 p.
7. Belyakov V.D., Semenenko T.A., Shraga M.Kh. Introduction to the epidemiology of human infectious and non-infectious diseases. - M.: Medicine, 2001. - 263 p.
8. Cherkassky B.L. Ethical and legal aspects of epidemiology. / Epidemiology and infectious diseases, 1996, No. 1. - S. 9-12.
9. Cherkassky B.L. Modern interpretation of the main categories of epidemiology. ZHMEI, 1991, No. 2. - S. 75-78.
10. Sinyak K.M. On the subject of epidemiology. ZHMEI, 1990, No. 7. - S. 82-86.
- Control questions (feedback):
- The main sections of the doctrine of the epidemic process
- Factors of the epidemic process are biological, social, natural. Their influence on the development of the epidemic process.
- The elementary cell of the epidemic process.
- Biological factor as an internal cause of the epidemic process.
- The value of natural and social factors in the development of the epidemic process.
- Definition of the concept of the source of infection.
- Types and categories of sources of infection.
- Determination of the pathogen transmission mechanism
- Phases and types of transmission mechanism.
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- The doctrine of the epidemic process. Classification of infectious diseases. Manifestations of the epidemic process. Social and natural factors.
Infectious diseases occur when a specific pathogen is introduced into the body, which, like any living microorganism, can only survive with continuous reproduction. The causative agent exists only when moving and changing owners.
An epidemic process is a continuous chain of successively occurring and interrelated infectious conditions (patients, carriers), manifested in the form of epidemic foci with one or more patients and carriers. This definition is fully applicable to anthroponoses, i.e. diseases in which the reservoir and source of infection is a person. In zoonoses and sapronoses, epidemic
Figure 1 Components of the epidemic process
The process is not chain, but fan-shaped. The epidemic process, or the process of the spread of infectious diseases among the population, is a complex, socially determined phenomenon, consisting of the interaction of three main elements: the source of infection, transmission routes, and a macroorganism susceptible to this infection (Fig. 1). These elements are closely interconnected and ensure the continuity of the epidemic process. When one of the factors is eliminated, the spread of an infectious disease stops.
Figure 2 Scheme of the transmission mechanism
Figure 3 Aerosol transmission mechanism
The aerosol turns into a drop-nucleolar one, in which there is a mass death of microorganisms. Large droplets quickly settle and dry up, turning into dust. Nucleoli with a particle size of less than 100 microns can stay in the air for a long time, move with convection currents inside the room and penetrate through corridors and ventilation ducts outside it. They sink slowly. When cleaning the premises, the movement of people and under the influence of other factors, a secondary dust phase of the aerosol is created. An important source of the formation of the dust phase of an infectious aerosol is sputum (in case of tuberculosis), as well as with additional localization of the pathogen in the body, for example, crusts of skin lesions. In the latter case, underwear plays a significant role in the formation of infected dust.
2. Intestinal (alimentary) infections - the pathogen is excreted in feces or urine, in some diseases (cholera) - and with vomiting. Infection occurs through the mouth. Water and food are the most important transmission factors (Fig. 4). In the body of children, the pathogen can enter through the mouth when sucking fingers or toys. Under poor sanitary and hygienic conditions, flies can become mechanical carriers of pathogens. An example of intestinal diseases is typhoid fever, shigellosis, cholera, etc. The primary factors for the transmission of the pathogen are various environmental factors that fall into the feces of patients. The path of pathogens isolated with faeces can be long, with a change in intermediate and final transmission factors. Elements of the environment that ensure the transition of the pathogen from one organism to another are commonly called infection transmission factors, and the combination of these factors that ensure the spread of the corresponding disease is called infection transmission. Usually, with the fecal-oral mechanism of transmission of pathogens, three ways are indicated: household, food and water. Such a division is based on the allocation of the final transmission factor. Certain types of pathogens with intestinal localization are characterized by a narrower organotropism.
Figure 4 Fecal-oral transmission mechanism
So, the causative agent of cholera multiplies in the lumen of the small intestine, the causative agents of dysentery - in the mucous membrane of the large intestine, the causative agents of typhoid fever - in the lymph nodes of the intestine with access to its lumen through the blood and biliary tract, the hepatitis A virus - in the liver tissue with access to the intestinal lumen through the bile ducts. Enteroviruses, in addition to the main localization in the intestine, are additionally localized in the upper respiratory tract. All this determines the originality of the epidemiology of individual nosological forms of infectious diseases with a fecal-oral transmission mechanism.
- Blood (transmissible) infections - the pathogen is in the bloodstream, and a blood-sucking carrier (lice, fleas, mosquitoes, ticks, etc.) is necessary for its transfer. Examples of such diseases are typhus, malaria, tick-borne encephalitis, yellow fever, etc. The unequal activity of carriers at different times of the year affects the level of infection and morbidity in people in different ways. In the body of carriers, a specific cycle of reproduction and accumulation of the pathogen can be traced (in lice - with typhus and relapsing fever, in fleas - with plague, in mosquitoes - with malaria). Finally, the pathogen can persist in the body of arthropods for a long time, being transmitted to offspring through laid eggs (transovarially). In this way, the tick-borne encephalitis virus is transmitted from one generation of ticks to another.
Infections of the outer integument - the pathogen is located on the outer integument (skin, hair, mucous membranes) or in the external environment. Infection occurs through direct contact, less often through contaminated objects, hands, soil, etc. These diseases include a variety of skin and venereal diseases, wound infections (tetanus, gas gangrene, etc.), as well as diseases associated with animal bites (rabies , sodoku).
The listed mechanisms of transmission of infectious diseases are typical for the spread of pathogens in natural conditions and are determined by the location of pathogens in the human body. In real life, artificial (artificial) ways of transmitting pathogens are also possible. Parenterally, you can become infected with infectious diseases in case of violation of the sanitary-hygienic and anti-epidemic regime in medical institutions through medical instruments and devices, blood transfusion, injections and other manipulations, accompanied by a violation of the integrity of the skin and mucous membranes. This mode of transmission is active among certain population groups, especially among drug addicts. Sometimes infections occur in unusual ways in laboratories, in the production of bacterial and viral preparations, etc.
susceptibility and immunity. Susceptibility is understood as the body's ability to respond to the introduction of an infectious agent with a number of specific pathological reactions. Susceptibility to infectious diseases is determined primarily by the unequal sensitivity of the organism to the introduction of a pathogenic agent. It depends on the state of the human body, its age, gender, on the qualitative characteristics of the pathogenic agent, its dose and the specific conditions of the place and time of development of the epidemic process. The infectious process is influenced by specific immunity and nonspecific resistance of the organism. A number of diseases, the so-called opportunistic infections (herpes, cytomegaly, toxoplasmosis, etc.), occur against the background of acquired or congenital immunodeficiencies. Post-infection immunity is formed in most cases after the transferred infections; with the introduction of active immunization agents (vaccines and toxoids), artificial immunity is formed.
Collective immunity is the ability of a collective to resist the damaging effect of an infectious agent. The immunostructure of the population (collective) consists of the distribution of individual members of the collective according to the level of susceptibility to a given pathogen. It reflects the state of immunity to a specific pathogen, acquired as a result of previous diseases, latent or active immunization.
Manifestations of the epidemic process.
Endemic morbidity, or endemia, is the incidence of a particular disease that is constantly recorded in a certain area, due to social and natural conditions.
Exotic morbidity - morbidity, unusual for the area. It occurs as a result of the introduction or importation of the pathogen from other territories. The ubiquitous distribution throughout the globe is characteristic of most anthroponotic infections and a number of zoonoses in domestic animals. The territorial uneven distribution of diseases is characteristic of zoonoses, the reservoir of which is caused by wild animals, and a number of anthroponoses, which is regulated by natural and social conditions. The territory of the spread of diseases is called the nosoarea. With a certain degree of conventionality, all infectious diseases can be combined into two groups according to the characteristics of their territorial distribution and type of nosoareal: with global and regional distribution. Global distribution is typical for most anthroponotic infections and a number of zoonoses in domestic animals. The regional spread of diseases is primarily characteristic of natural focal infections.
Depending on the intensity of the spread of the disease, the epidemic process can manifest itself in the form of sporadic morbidity, group diseases (epidemic outbreaks), epidemics and pandemics (Fig. 5). It is generally accepted that the main difference between the listed forms lies in the quantitative side of the issue, i.e. under
Figure 5 Manifestations of the epidemic process
Table 3. Grouping of anti-epidemic measures according to their focus on the links of the epidemic process
- Principles of immunoprophylaxis of infectious diseases. Immunobiological preparations.
Organizational and preparatory work
Preparing the population (conversations, lectures)
- Explanatory and sanitary-educational work.
Information about the time and procedure for vaccinations, their expediency.
Advice on washing the body and changing clothes before vaccination.
- Equipping rooms for examination, registration and vaccination.
Washing walls, floors, tables with hot water and soap or CMC, or wiping with a 0.2% chloramine solution.
Equipping with furniture, including a couch, in case of fainting.
Cabinet equipment for storage of first aid and emergency aid.
Acquisition of refrigerators for storage and transportation of vaccination preparations.
- Syringes, needles, scarifiers are sterilized and disposable.
- Application for vaccines.
Receipt of drugs from the Central State Sanitary and Epidemiological Service in advance, upon request.
Training of medical personnel
- Formation of vaccination teams.
Instructing vaccination teams on storage, dilution, method of administration of the drug, as well as reactions and complications during vaccination.
Record keeping - strict registration in the accounting and reporting documentation (individual and documentation of health facilities).
Checking the health status of medical staff (not allowed to be vaccinated with tonsillitis, respiratory tract infections, pustular lesions of the skin and mucous membranes, regardless of their location).
The appearance of the health worker - clothes (freshly ironed or sterile gown, cap); rings, bracelets, watches - removed; nails are cut short, hands are washed with soap, fingers are treated with alcohol or tincture of iodine. Washing is repeated after 12-15 injections.
- The optimal time is the end of the working day or week.
- Examination, questioning, thermometry of the vaccinated to identify contraindications.
Checking the label or labeling of the drug on the box, ampoule, vial, studying the data on the drug, expiration date, checking the integrity of the ampoules, compliance with the appearance requirements. In the absence of a label, the expiration date, a violation of the tightness of the ampoules, a change in the appearance of the grafting material (color, the presence of flakes, foreign inclusions, etc.), the drug should not be used.
The dry vaccine in the ampoule should be in the form of a powder or a homogeneous porous tablet. Wrinkling of the tablet, its inhomogeneity, wetting, discoloration or the formation of an uneven suspension with the addition of a solvent indicate the ingress of air and deterioration of the vaccine. Such a drug should be destroyed.
Killed bacterial vaccines and adsorbed toxoids are liquid preparations containing a clear supernatant and sediment. Serums and immunoglobulins are clear and slightly opalescent liquids. Non-adsorbed toxoids, toxins, liquid bacteriophages, inactivated leptospirosis vaccine, live polio vaccine are transparent. The adsorbed preparations are shaken before use to obtain a homogeneous suspension, but if the freezing and thawing of DTP vaccines adsorbed on aluminum hydroxide, ADS-, AD- and AS-toxoids occurs, their color changes, non-breaking flakes are formed. Vaccines lose their immunogenicity, cause strong reactions when administered.
The ampoules with the vaccine are opened before administration, having previously wiped the ampoules with the drug and the solvent with alcohol.
When the drug is administered intradermally, subcutaneously, intramuscularly, the skin is treated with 70% alcohol, after which it is lubricated with iodine tincture.
- When applying the vaccine on the skin, the skin is treated with alcohol, then degreased with ether. After scarification, this place is left open for 10-15 minutes for the absorption of the vaccine.
With intranasal administration of the drug, the nasal passages are preliminarily cleared of mucus. The vaccinated person must sit with his head thrown back, during the introduction of the vaccine he must take a deep breath, remain seated for another 2-3 minutes and do not clear his nose for 30 minutes.
- For children - a history of development, a card of preventive vaccinations and a certificate of preventive vaccinations.
For adults - a register of vaccinations and a certificate of preventive vaccinations.
- About implementation of inoculations in TsGSEN.
About strong reactions and complications in TsGSEN.
To the department of post-vaccination complications of GISC.
For most bacterial and viral preparations, the optimum temperature is from +3 to +10 ° C; they can be stored in household refrigerators.
As the temperature rises, many vaccines lose their specific properties; in live vaccines, cell death is accelerated. During freezing and subsequent thawing, the physicochemical properties of preparations change, irreversible processes occur that reduce immunological activity and increase reactogenicity. It is obligatory to observe the temperature regime during storage, transportation of vaccines before vaccination at all stages of the movement of drugs from the manufacturer until the moment of vaccination.
INDICATIONS FOR VACCINATIONS
Scheduled vaccinations
Vaccinations according to the national vaccination calendar (vaccinated contingents):
children:
- against tuberculosis, whooping cough, diphtheria, measles, mumps, poliomyelitis, tetanus, viral hepatitis B, rubella; military personnel:
- against tuberculosis, tetanus, gas gangrene, botulism; production workers who have contact with pathogens of infectious diseases;
population of natural foci of zoonotic and vector-borne infections:
- against tularemia, tick-borne encephalitis, etc.
Vaccinations according to epidemic indications according to the orders of the Ministry of Health of the Russian Federation:
the threat of the spread of diseases in a particular area:
(influenza, typhoid, cholera, etc.);
emergency vaccination for contact persons who may be in the incubation period of the disease: (measles, mumps, diphtheria, meningococcal infection, poliomyelitis, tetanus);
upcoming trip to a disadvantaged area:
(foci of tularemia, tick-borne encephalitis, yellow fever, etc.).
Contraindications to vaccinations are the same as for the planned appointment, but their number is limited or they are canceled.
Contraindications to prophylactic vaccinations
- Contraindications for vaccination are given in the table.
Selection for vaccination is carried out by examination by a medical professional and thermometry to rule out acute illness.
- Carrying out analyzes of urine, blood, especially immunological studies before vaccination is not required.
Refusal to vaccinate is recorded by the signature of the parents or two signatures of medical workers.
| Vaccine |
Contraindications |
| All vaccines |
Severe reaction or complication to previous vaccine administration |
| All live vaccines |
Immunodeficiency state (primary) Immunosuppression; malignant diseases pregnancy |
| BCG |
Birth weight less than 2000 g Keloid scar |
| DTP |
Progressive diseases of the nervous system History of afebrile seizures |
| Live vaccines against: measles, mumps, rubella, combined di- and trivaccines (measles-mumps; measles-rubella-mumps) |
Severe forms of allergic reactions to aminoglycosides For measles and mumps vaccines (especially foreign ones prepared on chick embryos): anaphylactic reaction to hen's egg protein |
| Hepatitis B vaccine |
Allergic reaction to baker's yeast |
- Acute infectious and non-infectious diseases, exacerbation of chronic diseases are temporary contraindications for vaccination.
Scheduled vaccinations are carried out 2-4 weeks after recovery, during the period of convalescence or remission.
For non-severe acute respiratory viral infections, acute intestinal diseases and other diseases, vaccinations are carried out immediately after the temperature returns to normal.
False contraindications
Unjustified withdrawal from vaccinations using diagnoses such as PEP and other stable or regressing neurological conditions, asthma, eczema, anemia, congenital malformations, thymus enlargement, long-term treatment with antibiotics, steroids, etc. Also, exemptions from vaccination of children who have undergone sepsis, hemolytic jaundice, pneumonia or having a family history of epilepsy, SIDS, severe vaccination reactions. Such references do not speak of the doctor's concern for children, but only of his medical illiteracy.
COMPARATIVE CHARACTERISTICS OF VACCINES
Vaccination - is carried out with the aim of artificially creating the body's immunity to infection to the introduction of specific antigens. By antigenicity, virulence, immunogenicity, method of obtaining the vaccine can be divided into the following main groups.
Live vaccines
Based on attenuated strains of viruses and bacteria. These are microorganisms with weakened or lost virulence, create a strong or long-term immunity, approaching post-infection in intensity: Ku, tick-borne encephalitis).
Inactivated vaccines
Microorganisms, inactivated:
- chemically (phenol, formalin, merthiolate, alcohol, etc.);
- physical means (high temperature, ultraviolet or gamma irradiation, etc.).
Whole cell vaccines have a complete set of antigens that form immunity against pertussis, typhoid, rabies, leptospirosis, influenza, herpes.
Subunit viral vaccines contain separate structural components of the virus - subunit influenza vaccine Influvac.
Disintegrated or split split vaccines, in which the lipid layer is removed, and the structural components are corroded by detergents - these are influenza vaccines - Vaxigripp, Fluarix, Begrivak, etc.
Chemical vaccines
Antigens of microorganisms maximally freed from accompanying substances using ultrasound, centrifugation, chromatography, gradient centrifugation, chemical agents against meningococcal infection (polysaccharide meningococcal groups A and C), typhoid fever (Vi-antigen of typhoid bacteria), brucellosis, cholera, typhus, flu, plague.
The relatively low reactogenicity of chemical vaccines is their main distinguishing feature.
Complex (associated) vaccines
Based on existing drugs - DPT vaccine, ADS and ADS-M toxoids, trivaccine (measles-rubella-mumps), etc.
Recombinant (genetically engineered) vaccines
The section of the gene of the microorganism responsible for the synthesis of a particular antigen is inserted into the plasmid DNA of the producing cells - the hepatitis B vaccine; or incorporation of the HIV gene into the nucleic acid of the variola vaccine virus.
Conjugated vaccines (antigen + polyelectrolyte)
The use of adjuvants, i.e., agents that non-specifically enhance a specific immune response, based on the conjugation of an immunizing antigen with synthetic polyelectrolytes. The immunogenicity and protective properties of vaccine antigens conjugated with polyelectrolytes increase by tens and hundreds of times with an increase in both antibody and cell-mediated immune responses. The domestic anti-influenza trivalent polymer-subunit vaccine Grippol and allergy vaccines have been developed and successfully used for 5 years. The development of conjugated polymer-subunit vaccines against brucellosis, typhoid, dysentery, tuberculosis and a number of other infections is nearing completion.
Anti-idiotypic (vaccines) antibodies
Used as antigens. Many fragments of the active centers of antigens have a "spatial similarity" with anti-idiotypic antibodies against them, so these antibodies can be used as a vaccine antigen, which immediately excludes the pathogenic and virulent properties of the pathogen, the vaccine and becomes non-reactogenic, harmless, but immune. The formation of T-B effectors of T-B immunological memory cells is possible, causing protection against this antigen.
Liposomal vaccines
Pathogenic antigens are contained in liposomes, one multi-chambered vesicles that are easily captured by macrophages, digested and quickly induce an immune response.
Synthetic vaccines
There are two ways to obtain such vaccines:
- natural active centers of antigens are “strung” on a synthetic thread, as a result, thymus-dependent antigens become thymus-independent, and in this way it is possible to “bypass” the genetically programmed insufficiency of the body's immune response to antigens;
binding of artificially synthesized antigenic determinants on natural carriers, which can be albumins, globulins and other macromolecular substances.
Based on the ribosomal fraction isolated from microorganisms and possessing immunogenic properties - that is, the ability to induce the synthesis of antibodies and protect macroorganisms from infection by certain pathogens. Ribosomal vaccines are highly effective preparations with a low level of toxicity, low reactogenicity and high immunogenicity, designed to prevent viral-bacterial airborne and intestinal infections.
Anatoxins
Chemically neutralized toxins of microorganisms against diphtheria, tetanus, gas gangrene, botulism, staphylococcal infection.
Promising new vaccines
Liposomal, genetically engineered, subunit, complex, conjugated, synthetic, anti-diotypic.
RULES FOR INTRODUCING VACCINES
Co-administration of vaccines. All vaccines given to a child by age are administered at the same time (in / m - in different parts of the body). BCG to avoid contamination of syringes and needles is injected before or
etc.................
EPIDEMIC PROCESS(Greek epidemos common among the people) - the process of the spread of infectious diseases in human society, which consists in the formation of a chain of epidemic foci that sequentially arise from one another. Epidemic process is the main object studied by epidemiology (see).
The epidemic process arises and is subsequently maintained only in the presence and interaction of three factors (elements, links): the source of the infectious agent (a sick person or animal, a person or animal - the carrier of the pathogen); ways and factors that ensure the transmission of the pathogen from an infected organism to a healthy one (for example, water, food, household items, blood-sucking arthropods); population susceptibility to a given infection (see Invasion, Infection). Providing a continuous change of generations of the pathogen, the epidemic process determines the existence of the pathogen as a species.
However, these, although the main factors of the epidemic process, are not in themselves either the epidemic process itself or its driving forces. They become driving forces only when social and natural conditions are included in their interaction, more precisely, when this interaction is mediated by appropriate social and natural conditions, which in different combinations can stimulate or inhibit the development of the epidemic process.
The decisive influence on the epidemic process is exerted by social conditions, such as the nature of economic activity and material security of the population, the nature of communication between people, population density, the level of improvement of settlements, working and living conditions, sanitary and hygienic skills, means of communication, mass movements of people, wars, hunger, health status. For example, rational water supply (see), sewerage (see) and cleaning of populated areas (see), if the population observes sanitary and hygienic norms and rules, can significantly reduce the incidence of intestinal infections. A huge impact on the nature and intensity of the epidemic process in many previously widespread infectious diseases is exerted by measures aimed at creating the most complete immune layer among the population, that is, the impact on the third factor of the epidemic process - susceptibility. In our country, immunoprophylaxis is strictly regulated, there is a calendar of preventive vaccinations (see Immunization), due to which the incidence of diphtheria (see), whooping cough (see), measles (see), polio (see) and many other infectious diseases has sharply decreased . The experience of the USSR in carrying out mass immunoprophylaxis, which ensured, in particular, the elimination of the incidence of smallpox in our country by 1936, was used by WHO in organizing a program to eradicate smallpox on a global scale, which ended with a complete victory over this formidable infectious disease (see Smallpox natural ).
Infections, the pathogens of which are transmitted by airborne droplets, spread most rapidly, often affecting (like influenza) in a short time in many countries and continents a lot of people susceptible to them. In diseases characterized by the fecal-oral mechanism of pathogen transmission, the epidemic process usually proceeds less intensively. However, in the presence of a large number of sources of infection or massive contamination of water or food by the causative agent of the disease, large epidemics of intestinal infections can occur, spreading over large areas.
The intensity of the epidemic process is characterized by the level of incidence and, depending on the frequency of cases of a particular infectious disease in a given area over a certain period of time, is estimated as sporadic incidence (see), epidemic (see) or pandemic (see). The term endemia (see) is not associated with the intensity of the epidemic process, but denotes the constant presence of people with a certain disease in a given area. In certain infectious diseases, the intensity of the epidemic process and its dynamics with a characteristic alternation of ups and downs in incidence both within one calendar year (seasonal phenomenon) and with an interval of several years (periodicity phenomenon) are quite typical. No less characteristic is the involvement in the epidemic process of certain predominantly affected age and occupational groups of the population.
The doctrine about epidemic process, being a basis of epidemiology (see), constantly develops and improves. Currently, considerable attention is paid to the study of the patterns of the spread of infectious diseases caused by opportunistic microorganisms (see), and slow viral infections (see).
The main methods of studying the epidemic process are epidemiological observation and experiment. When assessing the epidemic process, a number of generalized epidemiological indicators are used: intensive indicators (morbidity, mortality, mortality), characterizing the degree of development of the epidemic process from a quantitative side; extensive indicators - the distribution of the entire phenomenon under study into separate groups in accordance with one or another sign: for example, the division of all recorded cases of typhoid fever into three groups depending on the transmission factor of the pathogen (water, food, household items), the distribution of patients according to the severity of the course of the disease.
The main indicator characterizing the intensity of the course of the epidemic process is the incidence (see). This indicator is used to assess the level and nature of the distribution of cases of diseases within the study area, to determine the frequency of occurrence of the disease in different age and occupational groups of the population. Along with this, when analyzing the epidemic process, indicators of focality and severity of the clinical course of the disease, data on the sources and ways of spreading the infection are used (see Epidemiological indices). To determine the phenomena of seasonality and periodicity, morbidity rates are studied in dynamics - by months within one calendar year or by years within several years. When studying the action of any anti-epidemic factor, for example, the effect of prophylactic immunization (see) on the intensity of the epidemic process, the incidence rates are compared in groups of the population that are equal in quantitative, age and other characteristics, subjected to immunization and non-immunized.
Recently, in the domestic literature on epidemiology, the position on the self-regulation of the epidemic process has been discussed. At the same time, the epidemic process is actually considered as a biological phenomenon and, therefore, is likened to an epizootic process. It is possible that at the dawn of human development, the mechanisms of self-regulation of epidemic processes were similar to those observed during the development of epizootics in animal populations. However, as the socio-economic transformations of society, the epidemic process acquired a consistently increasing social character, along with which the importance of the mechanisms of its natural regulation was equally consistently decreasing. In historical terms, it is obvious that the intensity of the impact of the social factor on the patterns of distribution of various anthroponoses, that is, on the epidemic process, and hence on the mechanisms of its regulation, has consistently increased as the transition from one socio-historical formation to another. Thus, during the period of transition from the feudal system to the capitalist one, against the background of the widespread rapid development of large settlements that were not comfortable in sanitary and hygienic terms, mass migration of the population and the development of international trade, devastating epidemics of not only anthroponoses transmitted by airborne droplets (for example, natural smallpox) constantly arose. , but also infections with a more complex (fecal-oral or transmissible) transmission mechanism (for example, typhoid and typhus). In practice, these epidemics subsided only with a significant decrease in the number of people susceptible to this infection due to their death or the transfer of the disease.
Subsequently, public measures to increase the effectiveness of a set of sanitary and preventive measures, due to which the activity of the routes and factors of transmission of pathogens of a number of infectious diseases was sharply reduced or completely excluded and the population was immune to many of them, actually replaced the self-regulation of the epidemic process. An example of a radical impact on the mechanisms of regulation of the epidemic process in smallpox is the elimination of its pathogen as a species on a global scale, achieved with the help of rational immunoprophylaxis. The ability of society to eliminate a contagious disease is an additional argument in favor of the fact that the epidemic process in anthroponoses is deeply social in nature.
Bibliography: See bibliography. to Art. Epidemiology.
P. N. Burgasov, A. A. Sumarokov.
Within the framework of this section of the doctrine of the epidemic process, there are three theories: 1) self-regulation of the epidemic process; 2) the mechanism of transmission of pathogens of infectious diseases; 3) natural foci of infectious diseases.
The theory of self-regulation of the epidemic process was developed by Academician V.D. Belyakov and registered in the USSR as a discovery in 1976. This theory is a new theoretical concept of epidemiology about the internal mechanisms of the development of the epidemic process and makes it possible to rationally explain the temporal and territorial patterns in the spread of infectious diseases among the population.
The theory of the transmission mechanism was developed by L.V. Gromashevsky in the 40s. 20th century and describes the patterns of movement of pathogens of infectious diseases from person to person.
The theory of natural foci of infectious diseases, formulated by academician E.N. Pavlovsky in 1939, allows you to get an idea of the patterns and features of the spread of zoonotic infections among people.
The theory of self-regulation of the epidemic process. The main provisions of the theory of self-regulation of the epidemic process are:
- 1) heterogeneity (heterogeneity) of interacting populations of the pathogen and humans, which forms the basis for the development of the epidemic process;
- 2) dynamic (phase) change in the heterogeneity (heterogeneity) of the biological properties of interacting pathogen and human populations;
- 3) the stabilizing (controlling) role of negative feedback in the processes of self-regulation;
- 4) the regulatory role of social and natural conditions in the phase transformations of the epidemic process.
Among the signs heterogeneity characterizing the pathogen population, for the development of the epidemic process, it is primarily heterogeneity in virulence(i.e., according to the degree of pathogenicity of the pathogen). Heterogeneity in virulent properties is a universal characteristic of all pathogenic pathogens. At different periods of the spread of infectious diseases, pathogens circulate among people, differing in the degree and nature of heterogeneity in virulent properties.
The next most important feature of the pathogen population is heterogeneity in contagiousness. Contagiousness as the ability of a pathogen to spread among people and survival in the body of individual hosts is also a variable feature that changes during the development of the epidemic process.
Heterogeneity in immunogenicity characterizes the ability of the pathogen to cause certain forms of immunity in the host organism (antimicrobial, antitoxic, antiviral, humoral, cellular, local, general). Like contagiousness, immunogenicity is variable.
For the development of the epidemic process of individual infections, it is important heterogeneity of the pathogen population antigenic properties(flu), on its sensitivity to antibiotics(nosocomial infections), to bacteriophages(dysentery), etc.
It should be emphasized once again that the parameter of the pathogen population, which is of decisive importance in the development of the epidemic process, is heterogeneity in virulence. Heterogeneity in other characteristics is more often associated with virulence, although in some cases the development of the epidemic process is associated precisely with pathogens that are heterogeneous in characteristics independent of virulence.
For the development of the epidemic process, it is important heterogeneity human (host) populationby susceptibility to pathogens of infectious diseases. Susceptibility is a species trait, which is understood as the ability of the human body to respond to the pathogenic properties of the pathogen. In various periods of the spread of infectious diseases, the human population is made up of individuals who differ in the degree and nature of susceptibility to pathogens that cause these diseases.
The second position of the theory of self-regulation says that during the epidemic process, dynamic (phase) change in heterogeneity(heterogeneity) virulence in the pathogen population and susceptibility in the human population. Phase restructuring of interacting populations involves a successive change of four phases: 1) reservation; 2) epidemic transformation; 3) epidemic spread; 4) reservation conversion.
The population of the pathogen in the phase of epidemic spread is maximum. This phase causes the development of an epidemic, during which both non-immune persons and persons with partial immunity, which does not protect them from highly virulent (epidemic) variants of the pathogen, fall ill. The duration of the epidemic spread phase (epidemic duration) is always limited in time. This phase ends despite the presence of susceptible individuals in the human population. The epidemic spread phase cannot last indefinitely, primarily in the "interests" of the pathogen - otherwise it will exterminate all susceptible individuals and deprive itself of its habitat, as well as energy resources. Therefore, already in the phase of epidemic spread, the next phase is laid.
Reservation Conversion Phase begins with the passage of virulent variants of the pathogen through the body of immune individuals (who recovered from the disease and developed immunity during this epidemic). As a result, only those variants that have reduced virulence and adapted to the new (immune) habitat remain in circulation. In this phase, a significant part of the pathogen population dies, and the incidence of people is declining.
The fourth position of the theory of self-regulation reveals the regulatory role of social and natural conditions in the phase transformations of the epidemic process. Social and natural conditions that determine the phases of the development of the epidemic process can be divided into three groups: a) factors that cause the creation of various forms of "mixing" of people - the formation of teams, natural and artificial migrations; b) factors that cause the activation of the pathogen transmission mechanism; c) factors that reduce immunity and resistance. Any of the above conditions ultimately lead to an increase in the layer of highly susceptible individuals in the pathogen circulation chain, which serves as a signal for a restructuring of the internal organization of its population. On the other hand, the immunization of the team and the implementation of measures that reduce the activity of the pathogen transmission mechanism reduce the layer of susceptible individuals and are a condition for the formation of a reservation variant of the pathogen.
The theory of self-regulation of the epidemic process makes it possible to rationally explain the temporal and territorial patterns in the spread of infectious diseases among the population. The practical significance of this theory is that it focuses on the need for preventive measures in the reservation phase. At the same time, those measures that prevent the transition of the pathogen from the phase of reservation into the phase of epidemic transformation and epidemic spread will be rational.
The theory of the mechanism of transmission of pathogens of infectious diseases .
Transfer mechanism- this is an evolutionarily established process of moving a pathogen within one population from the organism of one host to a susceptible organism of another host, which ensures the preservation of the pathogen as a biological species in nature.
The transmission mechanism can be divided into three interdependent (interconnected) phases (Fig. 3).
The first phase - the removal of the pathogen from the source of infection - is determined by the localization of the pathogen in the macroorganism and is realized in a certain group of infectious diseases in the same way. For example, when a pathogen is localized in the intestine, only one way of removing it to the external environment is possible - by defecation, and when localized in the respiratory tract, there is also only one way of excretion - with exhaled air flows, i.e. while exhaling.
An infected human or animal organism, in which pathogenic pathogens can live, multiply, accumulate and be released into the external environment, is called the source of infection. That is, it is the natural habitat of the pathogen.
Among people, the sources of infection can be patients and carriers. The most important characteristics sick as sources of infection are the period of contagiousness and the severity of the clinical manifestations of the disease.
Considering the cyclical course of infectious diseases, it should be noted that during the incubation period in most infectious diseases, pathogens are not released into the external environment and, therefore, the infectivity of such individuals is excluded. However, if pathogens are isolated during the incubation period, this sharply increases the epidemic significance of such individuals as sources of infection and significantly complicates preventive work. This is due to the absence of clinical manifestations in the incubation period and the ability to identify such sources of infection. This situation is typical for viral hepatitis A and is one of the main reasons for the wide spread of this infection. During the height of the disease, the number of pathogens in the patient's body reaches a maximum. The virulence of pathogens that stand out against the background of clinical manifestations is significantly higher than in other periods of the course of the disease. Along with this, infectious diseases are characterized by such symptoms that contribute to the release of the body from pathogens (cough, runny nose - with aerosol infections; diarrhea - with intestinal infections, etc.). As a result, the peak period is characterized by the maximum release of the pathogen from the patient's body and this determines the greatest epidemic danger of infectious patients in the midst of clinical manifestations.
In the period of convalescence, in most cases, clinical recovery coincides in time with the release of the patient's body from pathogens. Sometimes, in some individuals, against the background of clinical recovery, the pathogen continues to be isolated and, naturally, they can be a source of infection for others.
Thus, patients present the greatest epidemic danger in the period of the peak of the disease. This is followed by a period of convalescence. In some infectious diseases, persons in the incubation period can also be sources of infection.
The epidemic significance of the severity of clinical manifestations is as follows. A patient with a severe form of an infectious disease, other things being equal, is a powerful source of infection, since he releases a large number of highly virulent pathogens. However, the severe course of the disease sharply limits the activity of such sources of infection and, ultimately, patients with mild clinical forms represent the greatest epidemic danger. The main reasons for the high epidemic significance of patients with mild forms are: a) in the structure of morbidity, as a rule, mild forms are more common than severe ones; b) patients with mild forms apply later or do not seek medical help at all; c) the diagnosis of such patients due to the uncertainty of the clinical picture is established later; d) isolation of patients with mild forms is less strict and is often carried out at home. The epidemic danger of patients with mild forms of infectious diseases increases even more if pathogens are isolated from the source of infection during the incubation period.
Carrying pathogens of infectious diseases- this is the isolation of the pathogen from the human body in the absence of clinical manifestations of the disease. According to the duration, transient, acute and chronic carriage is distinguished.
Transient carriage involves a short-term (most often single) isolation of the pathogen in the absence of clinical manifestations of the disease.
Acute carriage - isolation of the pathogen within a few days to two to three months. Acute carriage is predominantly a consequence of a recent illness.
Chronic carriage - the release of the pathogen for many months and even years. This type of carriage is also most often formed as a result of an illness in persons with defects in the immune system.
The degree of epidemic significance of these forms of carriage, other things being equal, is directly proportional to its duration. However, with individual infections under specific conditions, the role of acute carriers as sources of infection may be more significant than that of persons in a state of chronic carriage.
When analyzing the mechanism of development of the epidemic process in zoonoses, the concepts of "main" and "additional" sources of infection are used. The main source is the specific host of the pathogen, which ensures its preservation as a biological species (natural habitat). An additional source is a non-specific host of the pathogen capable of transmitting it to humans. A person with certain zoonoses (plague) can become an additional, in an epidemic sense, the most dangerous source of infection.
Reservoir of infection- set of pathogen populations in interaction with the natural habitat.
The second phase of the transmission mechanism - the stay of the pathogen in the external environment - depends on the method of removing the pathogen, which determines the environment into which it enters after being removed from the macroorganism. So, the pathogen that left the body of the source of infection during a conversation, coughing or sneezing, inevitably first of all gets into the air. The causative agent, released with feces, falls on various objects, which take part in its further spatial movement. Thus, the phase of the pathogen's stay in the external environment is inextricably linked with the phase of its removal from the source of infection.
To implement the phase of the pathogen's stay in the external environment, transmission factors are necessary, i.e. elements of the environment that ensure the movement of the pathogen from the source of infection to a susceptible organism. All elements of the external environment, acting as factors for the transmission of pathogens of infectious diseases, are divided into 6 groups: 1) air; 2) water; 3) food; 4) soil; 5) household items and industrial environment; 6) live carriers.
Elements of the external environment to which the pathogen enters when released from the body are called primary transmission factors, and those that deliver it to a susceptible organism are called final transmission factors. Sometimes both the primary and the final transmission factor is the same element of the external environment (for example, air). In some cases, the transfer of the pathogen from the primary factor to the final one is carried out with the help of intermediate transmission factors.
Certain types of pathogens are evolutionarily adapted not only to a specific localization in the host organism, but also to specific transmission factors. These are specific factors. The remaining factors are additional, but in certain specific conditions they can acquire important epidemiological significance.
The set of transmission factors involved in the movement of a specific pathogen from a specific source of infection to a specific susceptible organism is defined as the route of transmission infectious agent.
Various transmission routes are named according to the final transmission factor: airborne, water, food, contact-household and other transmission routes.
The third phase - the introduction of the pathogen into a susceptible organism - is determined by the previous phase (the stay of the pathogen in the external environment). And the nature and nature of the factors that introduce the pathogen into a susceptible organism determine the primary localization of the pathogen in the human body. The introduction of the pathogen into a susceptible organism is carried out during physiological (breathing, eating) and pathological (violations of the integrity of the skin and mucous membranes) processes.
Aerosol transfer mechanism - specific for pathogens of infectious diseases, primarily localized in the respiratory tract (Fig. 4.). In this case, the pathogens are released from the source of infection in the composition of droplets (aerosol droplet phase), which are concentrated around the source at a distance of 1-2 m, and the risk of infection decreases in proportion to the square of the distance from the source of infection. Large droplets settle quickly. The droplets remaining in the air dry up in the next 20 minutes after release. Only with an appropriate combination of temperature and humidity, they can last up to two hours or more. When drying, the droplet phase of the aerosol passes into the droplet-nucleolar phase. This is accompanied by mass death of microorganisms. Pathogens that are weakly resistant in the external environment die completely, more resistant - only partially. Nucleoli with particles smaller than 100 microns can stay in suspension for hours, move with convection currents inside the room and penetrate outside it through corridors and ventilation ducts.
Therefore, infection with pathogens that are part of the droplet-nucleolar phase of the aerosol is possible both in the room where the source of infection is located and outside it.
Large droplets that have settled on household items dry up, combine with dust, and as a result, a secondary dust phase of an aerosol containing pathogens is formed. The most important factor in the formation of the dust phase of bacterial aerosol is sputum. Dust particles smaller than 100 microns can remain in suspension for a long time, move with air currents to neighboring rooms and cause infection of susceptible persons.
The aerosol transmission mechanism is a very active mechanism, therefore, in the event of a source of infection, it provides almost universal infection of people. Due to the ease of implementation of this transmission mechanism (exhalation - inhalation), and the short residence time of pathogens outside a living organism, the vast majority of them spread by this mechanism have low resistance in the external environment. The aerosol mechanism transmits pathogens of diphtheria, measles, influenza, meningococcal infection, etc.
Fecal-oral transmission mechanism - is specific for pathogens of infectious diseases, the place of primary localization of which is the gastrointestinal tract (Fig. 5).
Pathogens are released into the environment with feces and spread mainly through three groups of transmission factors - food, water and household items. In some cases, flies (mechanical carriers) can be important in the transmission of pathogens of intestinal infections. A feature of the transmission factors (food products) within the fecal-oral transmission mechanism is that some of them serve as a favorable environment for the reproduction of pathogens. The accumulation of pathogens in such transmission factors causes infection of people with large doses of microorganisms and the development of severe clinical forms of diseases. Through household items and water, a small amount of pathogens is introduced into the human body, so the diseases associated with these transmission factors in most cases occur in mild forms. The scale of infection with infectious diseases, the causative agents of which are spread by the fecal-oral transmission mechanism, depend on the volume of consumption of food and water contaminated with their pathogens. Due to the fact that the implementation of the fecal-oral transmission mechanism requires a certain time, and the pathogens have to stay on the transmission factors for a long time, they must be highly resistant in the external environment. The causative agents of typhoid fever, dysentery, viral hepatitis are transmitted by the fecal-oral mechanism. A and etc.
Transmissive transmission mechanism - is specific for pathogens of infectious diseases, the place of primary localization of which is the blood (Fig. 6). When localized in the blood, pathogens have no way out of the body, so their further spread is possible only with the participation of blood-sucking arthropods. In the body of living carriers, either the accumulation of the pathogen or a certain cycle of its development occurs.
The main carriers are mosquitoes, lice, fleas, ticks, mosquitoes. Unlike factors of inanimate nature, live vectors actively attack people and, with a significant number, are able to provide a very high degree of their infectivity. Since pathogens transmitted by blood-sucking vectors practically do not come into contact with environmental factors, they do not require high resistance, therefore, most of them are characterized by weak resistance in the external environment. The pathogens of malaria, typhus and relapsing fever, etc., are transmitted by a transmission mechanism.
Contact transmission mechanism - is specific for pathogens of infectious diseases, the place of primary localization of which is the outer integument. The contact mechanism of transmission is realized when the affected areas of the skin of the source of infection come into contact with healthy areas of the skin (mucous membranes) of susceptible people. In this case, the transmission of pathogens is carried out by direct contact. The contact mechanism of transmission also includes the transmission of the pathogen to the skin (mucous membranes) of susceptible individuals through household items contaminated with pathogens (indirect contact).
The contact mechanism of transmission usually causes a limited spread of infectious diseases. In these cases, a narrow circle of people united by household premises and using common objects is involved in the epidemic process. The pathogens of tetanus, venereal diseases, etc. are transmitted by contact mechanism.
Thus, the localization of the pathogen in the body of the source of infection and its mechanism are mutually dependent phenomena, which, naturally replacing each other, form a continuous chain that ensures the preservation of the pathogen as a biological species in nature.
These transmission mechanisms ensure the spread of pathogens of infectious diseases among individuals of the same generation, i.e. are horizontal. Transmission of pathogens from mother to fetus vertical (transplacental) transmission mechanism . The vertical mechanism is the transmission of pathogens throughout the entire period of intrauterine development, i.e. from conception to the birth of a newborn. The most severe defects, deformities of the fetus are observed during infection at the stage of embryogenesis. Within the vertical mechanism, 4 transmission routes are distinguished: germinal (fetal), hematogenous - transplacental (hematogenous transfer of pathogens from the pregnant woman to the fetus during the prenatal period from the moment the embryo's own blood circulation is formed), ascending through the vagina and uterus (swallowing or aspiration of amniotic fluid contaminated by the pathogen from the 5th month), intranatal (infection of the newborn during the passage of the birth canal).
The epidemic significance of the vertical mechanism lies in the fact that children who become infected in utero from their mothers pose an epidemic danger to others. This is how pathogens of rubella, toxoplasmosis, herpetic, cytomegalovirus infections, etc. can be transmitted.
In the process of developing new methods for diagnosing, treating and preventing infectious diseases in medicine, a new mechanism for infecting a person with pathogens of infectious diseases has been formed. They called him artificial(artificiale- artificial), Fig. 7. The creation of large hospitals, a significant increase in the number of "aggressive" interventions, invasive diagnostic and treatment procedures, the formation of hospital strains and other factors contributed to the intensification of the artificial infection mechanism. Within the limits of the artificial mechanism of infection, inhalation (artificial lung ventilation, intubation) can be implemented; contact (non-invasive therapeutic and diagnostic manipulations); enteral (fibrogastroduodenoscopy, enteral nutrition); parenteral (invasive therapeutic and diagnostic manipulations) transmission routes.
Rice. 7.
The artificial mechanism of infection is not a transmission mechanism, since it does not correspond to the definition of this concept (an evolutionary process that is necessary for the existence of a pathogen as a species in nature). The causative agents of human infectious diseases, which are currently more often spread using an artificial mechanism of infection (HIV, viral hepatitis B, viral hepatitis C, and others), always have a natural main transmission mechanism, which determines their preservation as a species in nature.
It is possible to determine the type of transmission mechanism only by analyzing the nature of the spread of pathogens within a population of one species. The penetration of a pathogen from a population of hosts of one species (animals) into a population of hosts of another species (human) is not a transmission mechanism, since this movement is of no importance for the preservation of the pathogen in nature as a biological species. With regard to zoonoses, the transmission mechanism takes place only during the epizootic process. In relation to people, they talk about the mechanism (process) of infection or the ways of transmission of pathogens of zoonotic infections.
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