The route of transmission of infection through the blood is called. Ways of transmission of infection: how to protect yourself from the disease? An example of an infection with a fecal-oral transmission mechanism

Fecal-oral transmission mechanism

The law of epidemiology on the conformity of the mechanism of transmission of infection with the specific localization of the pathogen in the human body.

The localization of the pathogen in the body and the mechanism of its transmission from one host to another is a continuous chain of interdependent phenomena that ensures the preservation of the pathogen in nature.

Transfer mechanism - an evolutionarily developed way of moving a pathogen from one host organism to another, providing it with the maintenance of a biological species.

Transmission routes- a set of environmental factors that ensure the transfer of the pathogen from one organism to another in specific conditions of the epidemiological situation. Assessed by the final factor that served as the infection.

The mechanism of transmission corresponds to the main localization of the pathogen in the host organism.

Phases of pathogen transmission mechanism:

1. Isolation of the pathogen from the body

3. Introduction into a new organism

Transmission mechanisms:

1. Fecal-oral - gastrointestinal tract (typhoid fever, cholera, dysentery, HAV, HEV)

2. Aerogenic - respiratory tract infections (diphtheria, whooping cough, scarlet fever, measles, rubella ...)

3. Transmissible - pathogen in the blood (tularemia, HFRS, tick-borne encephalitis, malaria ...)

4. Contact - integuments, mucous membranes (anthrax, tetanus, rabies, foot and mouth disease, STIs)

5. Vertical

6. Artificial (artificial)

1-5 - natural mechanisms.

Transmission factors- elements of the environment that ensure the transfer of the pathogen from one organism to another

ü Food products

ü Live carriers

ü Household items

It is characteristic of intestinal infections, the causative agent of which is located in the digestive tract.

Transmission routes:

1. Alimentary (food) - salmonellosis, shigellosis, yersineosis, typhoid fever, etc.

2. Water - cholera, escherichiosis, HAV, etc.

3. Contact-household - shigellosis, escherichiosis, less often other OKI.

Transmission factors:

ü Plumbing

ü Well

ü Spring

ü Marine

2. Food products

ü Dairy (milk, sour cream, cottage cheese, butter, cheese, ice cream)

ü Cream

ü Meat (salmonellosis) - primary (when slaughtering livestock), secondary (infection of meat products with bacteriocarriers)

ü Beer (Shigella flexnera)

3. Household appliances (dishes, household items, dirty hands, toys, banknotes, common items)

Transmission routes:

1. Airborne - with microorganisms that are unstable in the external environment (meningococcus, SARS ...)

2. Air-dust - with stable, long-term viability (Mycobacterium tuberculosis)

transfer factor: air.

Phases:

1. The act of isolating the pathogen (when sneezing, coughing, breathing, talking)

Spray can

ü Drop phase (meningococcus, pertussis virus, measles, rubella, chickenpox)

ü Drying

ü Settling

ü Dust phase

2. Stay in the external environment

3. Penetration into a susceptible organism (inhalation)

This mechanism can be used as a bioterrorist act.

Topic 2

epidemic process. Mechanisms and ways of infection transmission. Anti-epidemic measures. Measures aimed at increasing the immunity of the population to pathogens. The human immune system, immunity and its types. Nonspecific and specific factors of human protection. Patterns of the formation of immunity in infectious diseases.

The founder of the doctrine of the epidemic process, Lev Vasilievich Gromashevsky, was the first to develop in detail the theory of general epidemiology, the concept of the source of infection, the mechanism of transmission and the driving forces of the epidemic.

epidemic process- this is the process of the emergence and spread among the population of specific infectious conditions - from asymptomatic carriage to manifest diseases caused by a pathogen circulating in the team.

The epidemiology of infectious diseases is the science of the patterns of occurrence and continuous development of the epidemic process and methods for studying it, continuously developing and studying preventive and anti-epidemic measures, organizing their implementation in practice to prevent the occurrence of infectious diseases among people, stopping these diseases in case of occurrence and for complete elimination of certain infections in certain administrative territories and on a global scale.

The epidemic process determines the continuity of the interaction of its three elements:

1. Source of infection;

2. Mechanisms, ways and factors of transmission;

3. The receptivity of the collective.

Turning off any of the links leads to the interruption of the epidemic process.

Epidemic focus- the location of the source of infection with the territory surrounding it to the extent that the infectious agent can be transmitted from it to others, i.e. the development of an epidemic process is possible.

Source of infection a living or abiotic object, which is the place of natural activity of pathogenic microbes, from which the infection of humans or animals occurs. The source of infection can be a human body (patient or carrier), an animal body and abiotic objects of the environment.

Anthroponoses are infections in which the source of infection is only a person.

Zoonoses are infections in which sick animals serve as the source of infection.

Sapronoses - infections in which the source of infection are environmental objects. (legionella - in evaporators of air conditioners or in showers, yersinia - on rotting vegetables in vegetable stores). Microorganisms must multiply on environmental objects to provide a sufficient infectious dose, which must be very large, as in all cases with opportunistic microbes.

Mechanisms, ways and factors of infection transmission.

Includes a sequential change of three stages:

removal of the pathogen from the body of the source into the environment;

stay of the pathogen in abiotic or biotic objects of the environment;

introduction (introduction) of the pathogen into a susceptible organism

There are five main types of transmission mechanisms of the infectious agent:

airborne (aerogenic)

contact

transmissive

Fecal-oral (alimentary)

vertical (including transplacental) (Gromashevsky)

aerogenic transmission mechanism- the mechanism of transmission of infection, in which pathogens are localized in the mucous membrane of the respiratory tract, from where they enter the air (when coughing, sneezing, etc.), stay in it in the form of an aerosol and are introduced into the human body by inhaling contaminated air.

Contact mechanism of infection transmission- the mechanism of transmission of infection, in which pathogens are localized on the skin and its appendages, on the mucous membrane of the eyes, oral cavity, genital organs, on the surface of wounds, come from them to the surface of various objects and upon contact with them by a susceptible person (sometimes by direct contact with source of infection) are introduced into his body.

Transmissible mechanism of infection transmission(also called "blood contact") - the mechanism of infection transmission, in which the infectious agent is located in the circulatory system and lymph, is transmitted by the bites of specific and non-specific carriers: the bite of a blood-sucking arthropod (insect or tick).

Fecal-oral mechanism of infection transmission- the mechanism of infection transmission, in which the localization of the infectious agent mainly in the intestine determines its excretion from the infected organism with feces (faeces, urine) or vomit. Entry into a susceptible organism occurs through the mouth, mainly by ingestion of contaminated water or food, after which it relocates to the digestive tract of the new organism.

vertical transmission route- in which the infectious agent is transmitted from mother to fetus during pregnancy and childbirth.

Types of vertical transmission of human diseases:

The development of medicine, new treatment technologies, the deployment of a network of healthcare facilities have led to the formation of a new, artificial mechanism for the transmission of infection - artificial, which is associated with medical, primarily invasive, therapeutic and diagnostic procedures.

Way of transmission- a form of implementation of the mechanism of transmission of infection from its source to a susceptible person (animal) with the participation of environmental objects.

Transmission factors- elements ext. environments (objects of inanimate nature) involved in the transmission of the infectious agent from the source to susceptible animals, but which are not the natural habitat of the pathogen.

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Chapter 3. Mechanisms and routes of infection transmission

Each infectious disease has its own way of transmission of microorganisms, which was formed in the process of evolution and is the main way to preserve the pathogen as a species.

There are three phases of the transition of the pathogen from one organism to another:

1) the release of a microbial agent from the body into the environment;

2) presence of the pathogen in the environment;

3) the penetration of the infection into a completely new organism.

Transfer mechanism infectious agents is carried out through these three phases, but may have its own characteristics depending on the primary localization of the pathogen. For example, when a pathogen is found in the cells of the mucous membrane of the upper respiratory tract, its release is carried out with exhaled air, in which there are microbial agents in the composition of aerosols (influenza, SARS, chicken pox, whooping cough, scarlet fever). When the infection is localized in the cells of the gastrointestinal tract, its isolation is possible with feces and vomit (dysentery, cholera, salmonellosis).

When the pathogen is in the bloodstream, the mechanism of its transmission will be blood-sucking insects (rickettsiosis, plague, tularemia, encephalitis). The contact mechanism is due to the localization of microbes on the skin.

Depending on the primary location of the pathogen in the human body, four mechanisms of infection transmission are distinguished:

1) airborne;

2) fecal-oral (food);

3) transmission;

4) contact-household.

Airborne(dust, inhalation) is one of the most common and fastest ways of transmitting infectious diseases. In this way, diseases caused by both viruses and bacteria can be transmitted. The concomitant inflammatory process of the mucous membranes of the upper respiratory tract contributes to the spread of pathogens. A large number of microbes are released with droplets of mucus when coughing, sneezing, talking, crying, screaming. The degree of power of this depends on the characteristics (most important particle size) of the aerosols. Large aerosols disperse over a distance of 2-3 m and quickly settle, while small ones cover a distance of no more than 1 m when exhaling, but can remain suspended for a long time and move considerable distances due to electric charge and Brownian motion. Human infection occurs as a result of inhalation of air with droplets of mucus contained in it, in which the pathogen is located. With this method of transmission, the maximum concentration of pathogens will be near the source of infection (patient or bacteriocarrier). As the distance from the source of infection increases, the concentration of microbes decreases significantly, but sometimes this is enough for the development of the disease, especially if the child is weakened and the pathogen has a high degree of pathogenicity. Cases are described in which the transmission of influenza, measles, and chickenpox viruses occurred over considerable distances, through ventilation, stairwells, and corridors. The airborne route of transmission depends on the stability of pathogens in the external environment. A large number of microorganisms quickly die when aerosols dry up (influenza viruses, chicken pox, measles), while others are quite persistent and retain their vital activity and properties for a long time in the composition of dust (up to several days). Therefore, infection of a child can occur when cleaning a room, playing with dusty toys, etc., such a “dusty” one is effective in diphtheria, salmonellosis, tuberculosis, scarlet fever, escherichiosis and other diseases.

fecal-oral The (food) route of transmission is realized in the transmission of intestinal infections caused by both viruses and bacteria. Transmission factors in this case are food products, dirty hands, contaminated water, flies, and various household items. Most often, however, infection occurs through contaminated food. So, it is possible to develop dysentery, salmonellosis, staphylococcal enterocolitis and intestinal infections caused by conditionally pathogenic microorganisms (which cause diseases under adverse conditions) - Proteus, Klebsiella, Pseudomonas aeruginosa. Less commonly, poliomyelitis, brucellosis, foot and mouth disease, scarlet fever, diphtheria, yersiniosis, hepatitis A, etc. are transmitted by the fecal-oral route. The development of diseases can occur when a person consumes meat and milk of sick animals that have not been subjected to good heat treatment (salmonellosis, foot and mouth disease, anthrax , tularemia), but the most common infection of people occurs when eating foods that contain the pathogen. Contamination of products is observed at different stages of their processing, preparation and further sale, which is more often associated with violations of the technological process and sanitary standards: through the hands of food industry workers, utensils, equipment, in contact with the contents of the gastrointestinal tract of slaughtered animals - carriers of infection, through rodents, etc.

Children become infected through milk and dairy products (cream, ice cream, sour cream, cottage cheese, cream). Dairy outbreaks of morbidity are typical for children's groups, they are distinguished by massiveness, a rapid increase in morbidity. Water plays an important role as a factor in the transmission of many infections: typhoid fever, hepatitis A, cholera, etc. The infection enters the water with the secretions of sick people and animals, with sewage, when sewage is washed off the surface of the earth by rain, etc. Most pathogens retains not only its properties in the aquatic environment, but also the ability to reproduce. From the point of view of epidemiology (the science of the spread of infectious diseases), closed water bodies are of great danger. Water epidemics are characterized by a rapid increase in the incidence among the population using water from one reservoir.

Contact household the mechanism of transmission is carried out either by direct contact (direct), or through contaminated environmental objects (indirect contact). As a result of direct contact, pathogens of diphtheria, tuberculosis, scarlet fever, herpes, scabies, helminths, and brucellosis are transmitted. With indirect contact through contaminated objects, linen, toys, dishes, the development of shigellosis, helminthiasis, typhoid fever, in rare cases - diphtheria, tuberculosis, scarlet fever. Most often, children become infected through contaminated hands. At the same time, a sick or bacterial carrier can contaminate household items - dishes, toys, doorknobs, railings, etc. A healthy child, using contaminated objects, easily contaminates his hands and brings the infection into his mouth.

As a transmission factor, soil is of independent importance in the transmission of anaerobic wound infections (tetanus, gas gangrene). The causative agents of these diseases enter the ground with the secretions of sick animals and people, where they form spores, maintaining their vital activity for several years.

The soil of Russia is 100% infected with tetanus. The development of the disease occurs when spores enter the wound surface (gas gangrene, tetanus) or food (botulism). The soil is also important in the transmission of infectious diseases because it is a place for the vital activity of flies, rodents and the maturation of helminth eggs.

Transmissible the route of transmission is carried out with the participation of a live carrier infected with the causative agent of an infectious disease.

Among the living, specific and non-specific carriers are distinguished. Specific - these are blood-sucking insects (lice, fleas, mosquitoes, ticks, mosquitoes, etc.). They transmit strictly defined infections. Pathogens in the body carry out their life cycle, multiply. Infection of a person occurs by biting or rubbing the contents of a crushed insect into damaged skin. So, lice carry out the transmission of typhus, fleas - plague, mosquitoes - malaria, ticks - encephalitis, relapsing fever.

Mechanical (non-specific) carriers transmit the infection in the same form in which they received it. For example, in flies on the paws and body there are pathogens of intestinal infections, hepatitis A virus, typhoid fever bacilli. The role of mechanical transmission in the spread of diseases is relatively small.

The intrauterine (transmission) pathway is one in which pathogens are transmitted from the mother to the fetus through the placenta. Infection in a pregnant woman can proceed either in an explicit form, or as a healthy bacteriocarrier. The most relevant transmission of viral infections through the placenta. Transition from mother to fetus is possible: rubella, measles, cytomegaloviruses, chickenpox, hepatitis B virus, mumps, enterovioruses. Bacterial infections can also be transmitted: escherichiosis, leptospirosis, streptococcal and staphylococcal infections, protozoal diseases: toxoplasmosis, malaria, leishmaniasis. The outcome of the fetus depends on the timing of infection of a pregnant woman (if a woman falls ill in the first three months of pregnancy, then more often the fetus dies or is born with malformations (embryonopathy)). If infection occurs after three months, fetal death or birth with signs of congenital infection is also possible. Intrauterine infection is important due to its severe course, frequent deaths and the risk of spread of pathogens in the maternity hospital or the neonatal unit.

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Chapter 2Chapter 4

1978 was officially marked by the discovery of the stamp of one of the most dangerous viruses in the world - HIV. Until now, scientists have not been able to overcome a deadly infection that destroys the human immune system. However, there is a therapy that can maximize the life of the patient (up to 15 years from the date of acquisition of the virus). There are several ways of getting infected, therefore, in order to prevent a death sentence, it is necessary to familiarize yourself with them and adhere to preventive measures.

Medicine knows three main ways that HIV infection enters the body:

1. Sexual(if there was sexual intercourse without barrier contraception).
2. Parenteral(upon contact with contaminated blood).
3. Vertical(the process of infection from mother to child, namely in the prenatal period, during childbirth and during feeding).

Attention! HIV infection cannot be transmitted through saliva during a kiss. Despite the fact that the virus is transmitted through most human fluids (semen, vaginal secretions, blood), its concentration in saliva is minimal.

During sexual contact

It has been determined that it is during unprotected sexual intercourse that HIV infection occurs most often. Semen or vaginal secretions contain enough virus to be transmitted to a healthy person. Therefore, if there was sexual intercourse without the use of a condom (the main means of barrier contraception that can protect against a deadly virus), then 100% infection can be confirmed. Once the virus enters the body, it is no longer possible to eliminate or block it.

It is important! A sufficient amount of the virus for infection is contained in the menstrual blood. When it enters the mucous membrane of the genital organs of a healthy person (if there are wounds), mandatory infection will occur.

Oral and anal sex - what is the danger?

Do not forget that oral and anal sex are not safe. With oral contact, if there are damages on the mucous membrane, then HIV can easily enter the body. Therefore, any oral sex with a carrier of the virus increases the risk of infection.

Anal sex is considered more dangerous. At the peak of HIV activation, homosexuals were the main carriers of the virus. This is explained by the fact that the rectum (precisely its mucous membrane) can be easily injured during penetration, therefore, a favorable condition is created for the direct entry of the virus into the bloodstream.

Risk factors for sexually transmitted infection

If a person has STDs such as gonorrhea, chlamydia, or syphilis, then the likelihood of infection is five times greater. In addition, it is women who are the main risk group, they are much more likely to become infected with HIV. This is explained by the fact that the area of ​​​​the mucosa (through which penetration into the body occurs) is much larger than in men.

This is dangerous! In semen, the concentration of the immunodeficiency virus is higher, so it is more dangerous for a woman to have sex with a sick man. In addition, vaginal secretions contain much less HIV infection.

When a woman has inflammatory processes, then unprotected sexual intercourse is prohibited in order to avoid infection with dangerous infections, as well as HIV. It has been established that with a diagnosis of uterine erosion, a woman becomes infected with the virus much more often. HIV infection is especially dangerous for women during menstruation.

Infection through the parietal route

The penetration of the virus occurs through the use of an infected syringe. Basically, drug addicts who practice injections with one syringe fall into the risk group. Contact of the needle with infected blood, and then with healthy blood, leads to HIV infection.

Note! HIV transmission through the use of a disposable needle has decreased to date, in line with the minimum prices for disposable syringes.

In medical practice, there have been cases of infection during surgical interventions, blood transfusions, and injections. However, in today's world there is practically no such possibility. All blood donors undergo a detailed screening for infection (particularly HIV and hepatitis viruses). For injections, only disposable syringes are used. When performing surgical procedures, instruments are used that undergo thorough sterilization and disinfection (several stages of processing).

Statistics! Almost half a percent of carriers of the virus are medical workers who became infected through careless contact with infected blood. Infection is not excluded even if the blood with the virus gets into the eyes.

vertical infection.

Most people, to the extent of ignorance, believe that an infected mother always gives birth to an infected child. However, scientists have found that in this case only 30% of sick children are born, the remaining 70% remain unaffected by the virus. Basically, infection occurs transplacentally, during the passage of the baby through the birth canal, as well as during breastfeeding.

It is worth considering that a child born to an infected mother is not diagnosed with HIV until the age of three. During these years, antibodies to the virus from the mother may remain in the child's blood. After three years, when they disappear, the child is considered healthy. If the child's body develops antibodies to a viral infection, the diagnosis of HIV is confirmed.

An increased risk of infection occurs if the mother has the following:

• HIV or the final stage - AIDS, manifests itself painfully in a woman;
• inflammatory processes are observed in the reproductive system;
• in the vaginal secret there is an increased concentration of the virus;
• negative social status (a woman leads an unhealthy lifestyle, eats poorly, refuses necessary therapy).

Reference! If the child is not full-term or is postponed, then the probability of infection is very high.

How can you not get infected?

There are many myths that claim false ways of getting HIV. To dispel misconceptions, you should read the detailed information.

In order to consult a doctor in a timely manner in case of infection and the use of the necessary therapy, you need to know the primary symptoms of HIV, a video will tell about it.

Video - The first symptoms of HIV

Infection prevention

Upon penetration into the body, the virus is activated in all biological fluids. But a sufficient amount to infect a healthy person can only be in semen, vaginal discharge (menstrual blood), blood, and breast milk. Therefore, there are several points of prevention:

1. Avoid contact with biological fluids.
2. Have sex only with trusted partners or always use barrier contraception.
3. Use only disposable syringes for injections.
4. If this is a medical worker, then with infected materials (blood, semen) must apply special protection methods.
5. During pregnancy, if a woman is a carrier of the virus, then special therapy is carried out to prevent infection of the fetus.
6. To prevent infection of the child during the passage of the birth canal, specialists perform a caesarean section.

Attention! Women who have been diagnosed with HIV are strictly prohibited from breastfeeding. It is best to raise a child on artificial nutrition.

If there is a suspicion of HIV or a risk factor for infection, then it is urgent to contact a specialist for further examination of the body. Suspicions should be caused by any atypical colds (thus, HIV manifests itself in the first stages). It is recommended to undergo an HIV test every six months, so that if the diagnosis is confirmed, timely use of ART therapy and slow down the viral processes in the body. Otherwise, if you refuse therapy, life expectancy is significantly reduced. Subject to the use of therapy and the observance of a healthy lifestyle, an HIV carrier can live a little more than fifteen years (cases of twenty years have been noted).