Infectious diseases

Among the many diseases that a person is subject to, there is a special group of diseases that are commonly considered infectious or infectious.

Infectious diseases are diseases caused by a live pathogen that have the ability to pass from a sick person to a healthy one, causing epidemics. Such pathogens, as a rule, are microorganisms - organisms that cannot be seen with the naked eye, but only with the help of more or less powerful microscopes.

But not all microorganisms pose a threat to human health. Some microbes can be inside the human body, without causing disease, and even helping the processes of life, such as digestion. According to this, all microbes on the globe are divided into three large groups by pathogenic microorganisms, that is, those that cause diseases can be:

Bacteria (cholera, sepsis, tuberculosis);

Viruses (flu, hepatitis, HIV);

Mushrooms (skin mycoses);

The simplest animals (dysentery, malaria)

Bacteria

Bacteria - unicellular pre-nuclear organisms. On Earth, there are more than three thousand species. They have microscopic dimensions (from 0.2 to 1 micron). The morphology of bacteria is quite diverse, according to which they are classified in a certain way according to their shape and ability to form groups. So, the following forms of bacteria are distinguished.

1. Monokoki. Grouping do not form. Have a spherical cell shape. Among them, rarely really pathogenic forms are found. The most common representatives of monocoque are micrococcus orange (Micrococcus aurentiacum) and micrococcus white (Micrococcus album), which in the case of reproduction form orange and white patches on food correspondingly.

2. Diplococci. There are several varieties. Often there is a combination of two bacterial cells of spherical shape, covered with a mucous membrane. This form has nitrogen-fixing azotobacter brown (Azotobacter croococcum), the causative agent of pneumonia (Dyplococcus pneumonius). There are also combinations of two cells that look like coffee beans. These include pathogens of gonorrhea (Neiseria honored) and meningitis (Neiseria miningitidis).

3. Streptococci. Spherical cells form long chains. Among them are found as non-pathogenic, such as those that cause souring of milk (Streptococcus lactis), and pathogens, which cause diseases of sore throat, scarlet fever, rheumatic heart disease. Their characteristic feature is that in the process of vital activity they secrete a c-reactive protein, which has hemolytic properties, i.e. those that destroy hemoglobin (Streptococcus piogenes).

4. Sarcins. Several spherical bacterial cells form small groups. A characteristic feature of this type of bacteria is the formation of spores and extremely rapid reproduction. Representatives include Sarcina flava, which forms yellow spots on consumer products, and Sarcina urea, which decomposes urine.

5. Staphylococcus. There are also pathogenic and non-pathogenic forms. For example, Staphylococcus aureus (Staphylococcus aureus) forms golden colonies in a nutrient medium and does not pose any direct threat to human health. However, there are a number of extremely dangerous staphylococci that cause severe inflammation: scarlet fever, sepsis. A colony of staphylococci is always a large collection of spherical cells. A characteristic feature of this group is its strong mutagenicity - the ability to form new forms.

6. Cocobacteria. A group of bacteria is extremely common in the environment. Cells are very small sticks, which are sometimes difficult to distinguish from micrococci. So, Pseudomonas lives in water and soil, which plays an important role as decomposers. In the gastrointestinal tract of humans and animals, conditionally pathogenic Escherichia coli (Esherichia Coli) lives, which, on the one hand, helps digestion, but, on the other hand, some of its forms can cause cholecystitis, pancreatitis. Among the causative agents of diseases can be distinguished Salmonela tiphi, which causes typhoid, Proteus vulgaris - anaerobic, which is the cause morbid condition  cavities (for example, maxillary).

7. Bacillus. Evolutionarily more advanced forms of bacteria, have a cylindrical shape and form spores. In addition, nutrients from the environment can always be used. Bacillus subtilis is a hay bacillus that multiplies rapidly in warm tea, Bacilus turingiensis is a bacterium that is of great importance for the development of environmentally friendly insecticides. It secretes a protein substance that causes paralysis of the intestinal apparatus of insects.

9. Streptobacilli. Like streptococci, they form long chains of their cells. There are pathogenic streptobacilli. So, Streptobacilus antracis is the causative agent of anthrax.

10. Clostridia. They have a spindle shape, they are characterized by anaerobic breathing. That is why most clostridia are pathogenic microorganisms. Clostridium tetani - the causative agent of tetanus, Clostridium botulinum - causes severe disturbance of the digestive organs - botulism, Clostridium septicum - the causative agent of gas gangrene. Clostridium perfringens is an indicator of fecal soil contamination. Living in the body, it enriches it with enzymes, but in the case of diabetes it can cause gangrene.

11. Vibrioes. They belong to the forms, which are sometimes called winding. Represent bent less than a quarter of a circle of sticks, slightly shaking. A typical representative of vibrioes is the causative agent of cholera Vibrio cholera, which sometimes forms colonies of blue color. Its peculiarity is that it only carries an alkaline medium (pH is greater than 7).

14. Mycoplasma. Interesting bacteria, because they do not have a cell membrane. ) X can be considered as a transitional form between viruses and cellular life forms. A characteristic feature is that they are completely incapable of living outside the host cell. Mainly mycoplasmas are represented by causative agents of plant and cattle diseases.

In addition to the classification of bacteria in the form of cells, a very important systematic feature is their coloring. At the heart of all methods for the classification of bacteria by color is their unequal internal chemical composition. The most generalized method of classification is gram stain. This method allows you to divide the entire huge number of bacterial organisms into two groups: gram-positive (turn purple after dyeing) and gram-negative (turn red after dyeing).

The practical significance of such a systematics lies in the unequal sensitivity of gram-positive and gram-negative bacteria to antibiotics. Thus, gram-positive bacteria are more sensitive to antibiotics of the penicillin series, and gram-negative bacteria - to antibiotics of the gentomicin and streptomycin series. This determines the treatment of infectious diseases.

There is an interesting feature of the spread of bacteria of different forms in the human body. By the percentage ratio between the types of microorganisms, you can determine the predisposition to a particular disease, prevent complications, and start treatment in time. A sample of the microflora taken from oral cavity, and its analysis can be easily done even at home with a microscope.

So, if streptococci and staphylococci dominate, this is evidence of respiratory diseases. If rod-shaped forms predominate (bacilli, streptobacilli, etc.), diseases of the gastric tract are possible. The appearance of diplococci - a sign of the disease of the genital organs, candida (branched chains of spherical bacteria) - an indicator of dysbiosis, possibly thrush, develops stomatitis. Spirochetes - satellites of the inflammatory process in the oral cavity. If all the bacteria are in approximately the same amount - there is no reason for excitement.

Viruses

The second group of common human pathogens are viruses. A virus is an autonomous genetic unit, capable of reproduction (reduplication) only in the host cell. Viruses can be considered as substances outside the cell. But, getting into the host organism, they begin to behave like living beings.

The structure of the virus is quite simple. It consists of a segment of nucleic acid (DNA or RNA) and protein molecules that perform the function of the shell (Fig. 49). The protein shell is enzymatically active, it provides the attachment of the virus to the host cell. Viruses are specific, they affect not only a particular type of animal, plant or human, but also certain host cells, so the polio virus infects only nerve cells and does not harm others.

Depending on the type of nucleic acid, DNA genomic and RNA genomic viruses are distinguished. To DNA genomic pathogens include hepatitis B, chicken pox, shingles. RNA-genomic viruses cause influenza A, B, C, measles and other diseases. Special group  viruses are the so-called retroviruses, which are represented by the well-known HIV - human immunodeficiency virus. HIV affects the cells responsible for immunity. In the event of infection occurs severe AIDS disease.

The mechanism of action of viruses is that, once in the body, they adsorbently penetrate into the host cell. Here there is a transition from an inert (crystalline) state to an active one. Next, the virus sheds its shell, freeing a segment of nucleic acid that is embedded in the genetic apparatus of the cell. Synthesis of virus components (nucleic acids, proteins) occurs. The newly formed particles tear the cell and go outside, damaging the nearest cells.

Vital activity of some viruses is quite specific. They can get into the human body, embed their nucleic acid in the DNA or RNA of the host cell. But, remaining in the cage, they are in a kind of symbiosis (the phenomenon of virogeny) and do not manifest themselves. Thus, vital activity is characteristic of retroviruses.

It is known that the main cause of cancer tumors is the action of just such viruses. The newly formed gene, which did not manifest itself for a long time, during nervous stress, effects of radiation, carcinogenic substances begin to function actively and cause the cell to synthesize stimulants of mitotic division. The appearance of extra proteins as a result of this leads to the formation of cancerous tumors.

Among other features of the life of many forms of viruses (for example, the causative agent of influenza) should be noted the so-called antigenic drift - mutations that occur in the pathogen every 2-3 years. The content of this process is to replace some part of the gene. Completely gene is replaced after 8-11 years. The value of this process is to counteract specific immunity. Interestingly, one virus, once in the human body, protects it from the penetration of other viruses. This phenomenon is known as virus interference.

A special group of microorganisms are phages - bacteria viruses. They are built more difficult, under an electron microscope it is clear that they have the form of a comma or a mace of 5-6 nm in size. They consist of a head, a rod, inside of which there are special contractile proteins, and several processes.

Phage affects both pathogenic and non-pathogenic bacteria, so it was thought that it could be used to treat infectious diseases. But it turned out that inside the human body the phage loses its activity. Therefore, it can only be used to diagnose bacterial infections.

Mushrooms

The body of the fungus (mycelium) may consist of one, highly branched cells, and in many. The main product of fungi is urea. Mushrooms reproduce extremely intensively, as a rule, with peculiar spores or budding.

Simplest and Worms

Another group of pathogens of infectious diseases are protozoa and worms.

To the simplest animals that cause diseases, include dysenteric amoeba, coccidia, sporozoans like. The body of the simplest animals consists of only one cell, which performs all the functions of the whole organism. Thus, a dysentery amoeba resembles a piece of protoplasm, constantly changing its shape, and can actively move. Once in the human body, it causes a serious illness of the digestive system - dysentery.

The cause of the disease is always the penetration into the human body of the pathogen in case of non-compliance hygiene rules, violation of cooking technology, contact with patients, etc.

Infectious diseases are known to mankind since ancient times, when vast territories, including entire states and peoples, were covered with epidemics. It is not without reason that infectious diseases are called "morovy diseases". Prevention of infectious diseases, the fight against them at all times and among all nations represented the most serious public problem.

Infectious diseases  - these are diseases that are caused and supported by the presence in the body of a lively damaging alien agent - the pathogen. It enters into a complex biological interaction with the human body, which leads to an infectious process, then an infectious disease. The infectious process is the interaction of the pathogen and the human body in certain environmental conditions, the body responds with protective reactions to the effect of the pathogen. The term "infection" means the state of infection of the body and manifests itself in the form of a disease or carrier.
  As a rule, each infectious disease has its pathogen. There are exceptions when a single disease may have several pathogens, such as sepsis. And on the contrary, one pathogen - streptococcus causes various diseases - sore throat, scarlet fever, erysipelas.

According to the localization of the pathogen in the human body, the ways of transmission and the methods of its isolation into the external environment, there are 5 groups of infectious diseases:

1. Intestinal infections (fecal-oral transmission). The pathogen is localized in the intestine and excreted into the external environment with feces, they can cause illness of a healthy person if they get into his body through the mouth along with food, water, or are carried with dirty hands. In other words, a fecal-oral transmission mechanism is characteristic of intestinal infections.

2. Respiratory tract infections (airborne - aerosol pathway). Infection of a healthy person occurs when infected mucus particles enter the respiratory tract.

3. Transmissible blood infections (pathogen transmission through carriers - mosquitoes, fleas, ticks, etc.). Pathogens penetrate into the bloodstream when bitten by fleas, mosquitoes, lice, mosquitoes, ticks, followed by localization of pathogens in the blood.

4. Blood infections are non-transmissible (infection by injection, transfusion of blood, plasma, etc.).

5. Infections of the external integument (contact pathway, infection through the skin or mucous membranes).

By the nature of the sources, infectious diseases are divided into two main groups: anthroponoses, in which the source of infection is humans, and zoonoses, when animals are the source of infection.

The main difference between infectious diseases and the rest is that the patient releases pathogens into the external environment, that is, is the source of infection and spread of infection. The release of the pathogen into the environment occurs in different ways: with exhaled air when coughing and running nose, with urine, with feces, etc. It depends on the location of the source of infection in the body.
  Infectious diseases are always accompanied common reactions  of the body: fever, fever, toxic damage to the nervous system, etc. In some infectious patients, even neuropsychic disorders can develop.
  Infectious diseases are very dynamic - the symptoms of the disease can quickly replace each other. For example, a skin rash quickly appears and quickly disappears, stool disorders persist only for a few hours, signs of dehydration also increase fairly quickly, etc. Due to frequent changes of symptoms, difficulties may arise in diagnosis.
  Another feature of infectious diseases is that the absence of complaints is often ahead of the full restoration of all functions disturbed by the disease. Very often, in the recovery period, significant changes in individual organs and systems are preserved: the heart after diphtheria or tonsillitis, the colon in dysentery, the liver in viral hepatitis, the kidneys in hemorrhagic fever, etc.

When meeting with pathogens of infectious diseases, people do not always get sick. This may be due to the innate or acquired resistance of a number of people to pathogenic microbes. Important in protecting against infectious diseases is the constant observance of preventive measures.
  In the human body, the body's protective barriers stand in the way of the penetration of pathogenic microbes: dry clean healthy skin, hydrochloric acid and stomach enzymes, and leukocytes (white blood cells) in the blood, which seize and destroy pathogenic microbes. In a healthy body, the defenses are more effective.
  The main causative agents of infectious diseases are: protozoa, bacteria, spirochetes, rickettsia, chlamydia, mycoplasmas, viruses, etc. Most infectious diseases are caused by bacteria and viruses.
  Several major factors are involved in the transmission of pathogens: air, water, food, soil, household items, live vectors.
Air serves as a factor in the transmission of the so-called drip infection, i.e. participates in the mechanism of transmission of pathogens of respiratory tract infections. The pathogens enter the air with droplets of mucus in large quantities during sneezing, coughing and talking. In suspension, they are within a few hours and can be transported with a current of air to other rooms and deposited on the surrounding objects. After the drops of mucus and sputum have dried, the pathogens get into the dust and get into the body of a healthy person with inhaled air. Thus spread tuberculosis, anthrax, tularemia.

Infectious diseases  - these are diseases that result from the penetration of pathogenic (pathogenic) microorganisms into the human body.

The main causative agents of infectious diseases are: prions, protozoa, bacteria, spirochetes, rickettsia, chlamydia, mycoplasmas, fungi, viruses, etc. But most infectious diseases are caused by bacteria and viruses.

However, sometimes, a simple penetration into the body of a pathogen is not enough for an infectious disease to develop. The human body must be susceptible to this infection and must respond to the introduction of the microbe with a special reaction that determines the clinical picture of the disease and all its other manifestations. And in order for a pathogenic microbe to cause an infectious disease, it must have virulence ( poisonousness; lat virus - poison), that is, the ability to overcome body resistance and exhibit toxic effects. The pathogen enters into a complex biological interaction with the human body, which leads to an infectious process, then - infectious disease .

In the human body, on the path of penetration of pathogenic microbes, protective barriers of the body are always on guard: healthy skin, hydrochloric acid and stomach enzymes, blood leukocytes (white blood balls of blood) that capture and destroy pathogenic microbes.

How do pathogens act?   Some pathogenic agents cause poisoning by exotoxins (for example, tetanus, diphtheria) excreted by the body during life processes, while others simply release toxins (endotoxins) when their bodies are destroyed (for example, cholera, typhoid fever).

Transmission of an infectious agent can occur through direct contacts (horizontal transmission of the pathogen), as well as through the placenta from the mother to the fetus (vertical transmission of the pathogen).

As a rule, each infectious disease has its own specific pathogen, but sometimes there are exceptions, when one disease can have several pathogens (sepsis). And, on the contrary, when one pathogen (streptococcus) causes different diseases (for example, sore throat, scarlet fever, erysipelas). Every year, new pathogens of infectious diseases are discovered.

Infectious diseases are characterized by:

1. etiology (pathogenic microbe or its toxins);
  2. infectiousness, often - a tendency to widespread epidemic spread;
  3. cyclical flow;
  4. formation of immunity;

In some cases, they are characterized by the possible development of micro carrier or chronic forms of the disease.

In addition to pathogenic microorganisms, there are also such microorganisms that are found both in the environment and in the composition of the normal human microflora. They are called   conditionally pathogenic microorganisms (UPM) . OTP is usually harmless to a healthy person. But in immunocompromised patients, UPM can cause endogenous or exogenous infections after penetrating organs and tissues, where their existence is usually excluded. A type of endogenous infection is autoinfection, resulting from the spread from one source of the host organism to another.

Many pathogens of infectious diseases are visible under a conventional microscope, and sometimes they can only be seen when magnified thousands of times through an electron microscope.

There are several periods in the development of an infectious disease - this is the incubation period, the initial period, the height of the disease and recovery. Each period has its own characteristic features.

One of the features of infectious diseases is the presence of incubation period .

Incubation period   - time from the moment of infection to the first clinical manifestations  diseases. Different infectious diseases have a different duration of this period from several hours to months, and even years. For some diseases, the duration of the incubation period is strictly defined.

Table. The duration of the incubation period of infectious diseases

Initial period   - This is the time from the moment the first signs of the disease appear to its height. No in this period characteristic signscommon to a particular disease, common symptoms of the disease prevail.

The height of the disease   - the appearance of characteristic of this disease symptoms, many signs can reach its maximum severity.

Recovery period   It starts from the moment when the manifestation of an infectious disease decreases, the duration of which depends on many factors: the severity of the illness, associated diseases, the characteristics of the organism, etc.

Sometimes, after an infectious disease is postponed, residual effects are observed, usually occurring during the height of the peak, but persisting for many months, years, and even the whole life.

Classification of infectious diseases

Today, the most widely used classification of infectious diseases L. V. Gromashevsky:

• intestinal (cholera, dysentery, salmonellosis, escherichiosis);
• respiratory tract (influenza, adenovirus infection, whooping cough, measles, chicken pox);
• “Blood” (malaria, HIV infection);
• outer covers (anthrax, tetanus);
• with different transmission mechanisms (enterovirus infection).

When meeting with pathogens of infectious diseases, people do not always get sick. This may be due to the innate or acquired resistance of a number of people to pathogenic microbes. Important in protecting against infectious diseases is the constant observance of preventive measures to prevent infection.

Preventive measures include:

• increase the body's resistance to hygiene and physical education;
• conducting preventive vaccinations;
• quarantine activities;
• cure infection source.

Quarantine   - This is a set of measures to stop the spread of infection, this includes the isolation of previously ill, disinfection of the place of residence, the identification of contact with patients, etc.

Infections do not recognize geographic barriers and state borders. An epidemic that has erupted anywhere in the world poses a threat to residents of other countries. Active immunization makes it possible to dramatically reduce the incidence of infections and completely eradicate some of them. In the latter case, vaccination becomes unnecessary, as happened with smallpox.

The evolution of man as a biological species is connected with his continuous struggle for existence with his eternal enemies - the most aggressive elements of the external environment - microorganisms .

Russian chronicles brought us terrible reports of mass epidemics - the pestilence. In the hordes of nomads, rushing to Russia in 1060, an epidemic of unknown disease arose; the same plague swept over the troops of the princes Izyaslav, Svyatoslav, Vsevolod, Vseslav, who fought against the invaders. The epidemic in Polotsk in 1092 quickly spread to Kiev and within three months destroyed 9 thousand inhabitants and soldiers. In Smolensk from the Mora 1230 - 1231 years. 32 thousand people died.

The search for the enemies of humanity and the means to combat them does not stop for a minute. In place of defeated microorganisms and diseases, others appear, often more sophisticated. One example of this is the virus. Aidsand the giant “silent” pandemic of the 20th century that it caused, which in the course of 20-30 years of this century can destroy at least half of the world's population.

The activity of the epidemic process changes under the influence of natural and social conditions.

Natural conditions include climate, landscape, animal and plant life, the presence of natural foci of infectious diseases, natural disasters, etc.

Social conditions are commonly understood to mean the totality of people's living conditions: population density, housing conditions, sanitary and communal improvement of human settlements, material well-being, working conditions and cultural level of people, migration processes, the state of the health care system, etc.

The emergence and expansion of the epidemic process is possible with the continuous presence of three components: the source of infection, the mechanism of transmission, and human susceptibility.

Infected people and animals that are natural carriers of infectious diseases, from which pathogens can be transmitted to healthy people, are called sources of infection.

The relationship between patients who are distributors of infection and healthy are built along two main chains: the patient — the causative agent — healthy, or the bacterium carrier (the virus carrier) —the causative agent — healthy. Bacterial carrier (virus carrier) can be observed after a clinical recovery for a long time (with typhoid fever, dysentery, scarlet fever, diphtheria, meningitis, polio, etc.), sometimes even years.

Susceptibility - the ability of the human, animal, plant to respond to the introduction, reproduction and activity of harmful (pathogenic) microorganisms, to the development of the infectious process with a complex of protective and adaptive reactions. The degree of susceptibility depends on the individual ability (reactivity) of the organism to resist the disease, determined by general, non-specific individual and specific (immunity-related) protection factors.

Under the transmission mechanism pathogenic microbes  the set of evolutionarily established ways of moving pathogens from an infected organism to a healthy one is understood. The mechanism of transmission of the causative agent (infection) includes: elimination of the pathogen from the infected organism, its presence during one or another period in the external environment and the introduction of the pathogen into the organism of a healthy person or animal.

Are known six major transmission mechanisms :

1. Food (alimentary ). Any food (poorly washed vegetables and fruits, meat, milk, dairy products) contaminated with feces and urine of animal carriers contaminated with pathogenic microbes can be transmitted to intestinal infections, “dirty hands diseases” - typhoid fever, cholera, dysentery, salmonellosis, brucellosis, Botkin's disease, anthrax, etc. Botulism occupies a special place in this series, the causative agent of which multiplies rapidly and secretes toxin in such products as canned food, sausage, mushrooms, salted fish, cooked in violation of technology Expensive at home).

2. Water. In violation of sanitary and hygienic rules and norms of water supply, drinking raw water, washing dishes, vegetables and other products with water contaminated with sewage, manure of livestock farms, etc., as well as bathing, diseases of cholera, typhoid fever, dysentery, paratyphoid fever are possible. , brucellosis, tularemia, etc.

3. Airborne . When coughing, sneezing, talking, during expiration, kisses, infections with the flu, acute respiratory diseases, pulmonary tuberculosis, as well as meningitis, measles, diphtheria, whooping cough, scarlet fever, rubella, parotitis (“mumps”), smallpox, ornithosis, etc.

4. Air dust . When the sputum and feces dry up, the microorganisms settle on the smallest dust particles, which then rise by air currents and “float” in the air (microbes are especially dangerous and can form spores that can exist for a long time in adverse environmental conditions). Inhalation of infected dust particles can cause diseases such as smallpox, pulmonary tuberculosis, pneumonia, and tetanus; through the fur and skin of animals can be infected with anthrax, intestinal infection, worms eggs; infection by microscopic mites living on dust particles is also possible.

5. Contact and household.   Contact with the patient or with his discharge (less often with the items he used - dishes, linens, toys, books, etc.) may be infected with the flu, scarlet fever, dysentery, typhoid fever, etc., during contacts with fur products - anthrax.

6. Through transmitters: lice - typhus, recurrent typhoid lousy; ticks - encephalitis, recurrent tick-borne typhus; fleas, rodents (gophers, mice, rats, tarbagans) - the plague; flies - gastrointestinal diseases; mosquitoes - malaria; cockroaches - typhoid fever.

Ways of transmission of infection are the basis for the classification of infectious diseases.

Each infectious disease is caused by a specific pathogen. The causative agents of infectious diseases differ sharply from each other in their resistance to the environment: some die in a very short time (in a few hours), others can survive days, weeks, months, and even years. From several days to several months, microorganisms that cause typhoid fever, dysentery, and cholera remain viable in the environment.

For most pathogens of diseases, their habitat is soil, water, plants, wild and domestic animals.

The causative agents of botulism, tetanus, gas gangrene, and some fungal diseases constantly reside in the soil. Infection through the soil can occur under various circumstances, even during children's games on the sand. Particularly dangerous to hit the ground on the affected areas of the body.

Botulism -   severe infectious disease, accompanied by symptoms of general poisoning of the body. Called food products infected with botulinum bacteria. Urgent administration of antibotulinic serum is required.

Tetanus - an acute infectious disease, the causative agent of which enters the soil from the intestines of animals or humans and remains in it for a long time in the form of spores, penetrating into the body through damaged skin or mucous membranes. It is manifested by agonizing general convulsions, spasms of the respiratory muscles are possible. Apply preventive and extreme (after damage to the integument) vaccinations.

Gas gangrene   - A severe complication of wounds caused by anaerobic microbes, accompanied by the death of tissue, organ, part of the body and general poisoning of the body.

Leptospirosis - an acute infectious disease that affects the small blood vessels - capillaries, as well as the liver, kidneys. Pathogens are microorganisms of the genus Leptospira (have the form of a thin helix) that live for a long time in water.

Up to 80% of diseases are caused by poor drinking water and sewage faults. Water epidemics can occur when the water supply system is polluted by the city's sewage water, and when water is supplied by groundwater.

Typhus - The common name of some infections, accompanied by fever, disorders of consciousness, lesions of the heart, blood vessels, central nervous system (typhus), intestines (typhoid fever). Typhoid and paratyphoid A and B are caused by Salmonella. These bacteria are quite stable in the environment. Once in the human body, the pathogens are deposited on the mucous membrane of the small intestine, where they accumulate and multiply, and then they enter the blood.

Dysentery - an infectious disease that is caused by bacteria from the intestinal family - infects the large intestine and causes poisoning - intoxication of the body (weakness, indisposition, headache, fever, nausea). Transmitted mainly through contaminated food and water, as well as with dirty hands. With adverse hygiene conditions, dysentery can take epidemic spread.

Type A viral hepatitis (botkin's disease) is a human infectious disease that is caused by a specific virus and occurs with a primary lesion of the liver. Clinically, viral hepatitis A is manifested by symptoms of general intoxication, impaired liver function and the development of jaundice, and a metabolic disorder. The mechanism of transmission is through food and in violation of sanitary standards in the bathrooms.

Viral hepatitis type b   distributed mainly during various medical procedures (blood transfusions, injections, etc.).

The causative agents of airborne infections (influenza, diphtheria, etc.) get from a patient to a healthy one through the air when coughing, sneezing, talking.

Flu - acute infectious viral disease. It is clinically characterized by fever, general intoxication syndrome and inflammation of the mucous membranes (catarrhal) of the upper respiratory tract, especially the trachea.

Tuberculosis relates to social diseases, the occurrence of which is associated with living conditions. The causative agent is Mycobacterium tuberculosis, or Koch sticks. Under natural conditions in the absence of sunlight, they remain active for several months, in street dust - up to 10 days, on paper - up to 3 months, in water - up to 150 days, they withstand rotting processes. Koch's wand is transmitted mainly by airborne droplets. Tuberculosis affects various organs and tissues of the human: lungs, eyes, bones, skin, urinary system, intestines, etc.

Cholera - an acute infectious disease in which the body is dramatically dehydrated. Cholera vibrio for a long time maintains vitality in the environment. Cholera disease is characterized by the sudden onset of abundant diarrhea and vomiting, leading to severe dehydration and desalination of the body, severe impairment of blood circulation, cessation of urination, a decrease in body temperature, the appearance of seizures, deep metabolic disturbances and depression of central nervous system functions up to the development of coma.

The only source of spread of cholera pathogens is people who emit cholera vibrios into the external environment, mainly with feces and less often with vomit masses. The main route of spread of cholera pathogens is infection of water with secretions of carriers of cholera vibrios.

People or domestic animals entering the territory of the natural source of infection - the habitat of the causative agents of tularemia, plague, tick-borne or mosquito encephalitis, or typhus - can become infected with these diseases.

Yellow fever - an acute infectious disease caused by a specific virus and transmitted by mosquitoes of strictly defined species with limited natural geographic distribution. It is clinically characterized by general intoxication of the body, two-wave fever, and can cause jaundice and kidney damage. The source of infection is a sick person, from which the virus enters the mosquito.

Tularemia - Infectious disease, accompanied by fever and lymph nodes (buboes). The pathogen is a bacterium; it dies when heated to 60 ° C in 20 minutes, when boiling it immediately.

There are diseases in which transmission of a contagious onset occurs through contact without the participation of a carrier: when attacking and biting animals (rabies), or through water, or by airborne droplets (plague, ornithosis).

Rabies - an infectious disease, affects the nervous system, accompanied by convulsions, paralysis, as well as spasms of the pharyngeal and respiratory muscles. The causative agent is a virus. Prevention in humans: emergency vaccinations after a bite.

Plague - A particularly dangerous infectious disease, which is caused by microbes - plague sticks. Its signs are: the general serious condition of the patient, inflammatory process  in lymph nodes, lungs and other organs. Disease plague without proper treatment is quickly fatal. In our country, the main carriers of plague infection are gophers, and the main link in the transfer of plague diseases from wild rodents to humans are rats. The main carriers of plague pathogens from rats to humans are rat fleas. Transmission of a plague infection can occur not only when a person is bitten by a flea-infected person, but also when flea stool gets on its skin or mucous membranes.

Ornithosis - group of infectious viral diseasesaffecting birds and transmitted to humans. In humans, there is a fever, headache and muscle pain, and pneumonia.

The greatest risk of infection by these diseases is exposed to people who first came to the territory of a natural hearth, for example, townspeople who spend rest time in places where there are foci of certain diseases. Locals usually get sick less often, because they often develop immunity as a result of frequent contact with pathogens. And even if they get sick, the disease is mild.

Tick-borne encephalitis virus immunity is observed in 90-100% of local residents of taiga villages in the south of the Krasnoyarsk Territory.

Forest ecosystems inhabit many species of ticks that are carriers and keepers of the virus that causes tick-borne encephalitis.

Encephalitis- inflammation of the brain; caused by viruses.

Tick-borne encephalitis  - A disease affecting the central nervous system. The favorite habitats of ticks are southern taiga forests throughout the European and Asian parts of Russia.

Infectious diseases are dangerous because their pathogens, emitting toxic substances for the body (toxins), affect various systems of human organs .

During the course of an infectious disease, there are successively alternating periods: latent, onset of the disease, active manifestation of the disease, and recovery. The time from the moment of introduction of the pathogenic microbe into the body and until the first signs of the disease appear is called a hidden (incubation) period. The duration of this period varies from several hours to several weeks and even months. At this time, there is not only the reproduction of microbes, but also the restructuring of protective mechanisms in the human body.

During the first period, the second develops, in which the first symptoms of the disease are detected, but there is still no specific manifestation of the disease.

The characteristic symptoms of the disease are fully manifested only in the third period. In this period, in turn, we can distinguish the initial stage, the height of the disease and the stage of subsidence of all pathological manifestations. The fourth period is characterized by the restoration of normal body functions.

Most infectious diseases develop cyclically, i.e. there is a certain sequence of development, increase and decrease of symptoms of the disease. Infectious disease in different patients can occur in various forms. So, there are lightning, acute, subacute and chronic forms of the disease.

(see), etiol. agent, the cause of infection. diseases. B. 6. There may be viruses, bacteria, fungi, protozoa and metazoa. Accordingly, this infection. diseases are divided into viral, bacterial, fungal (mycoses), protozoal and parasitic. B. Ability b. cause disease depends on its pathogenicity and virulence, infectious dose, the place of penetration into the body, the susceptibility of the host organism to this microbe. B. criteria b. different for obligate and conditionally pathogenic microbes. The main criteria for B. b. for obligate pathogenic microbes - the release of a clean edge (regardless of quantity) from the primary and / or secondary pathological focus (see Bacteriological method);detection in an organism specific to this microbe immunol. shifts, for example, increases in the titer of Ab (see Serological method)or body sensitization (see Allergic method);the presence of signs of the disease characteristic of microbial diseases. Auxiliary value in some cases may be the reproduction of a wedge, picture or its supporting symptoms on laboratory animals (see Experimental method).In assessing V. b. it is necessary to exclude the carrier state that coincides with the disease of the same organ, but other etiologies (for example, the carriage of corynebacterium diphtheria in b-ny streptococcal angina), as well as the presence of At and sensitization caused by a previous disease or vaccination. B. criteria b. for conditionally pathogenic microbes(see), especially in diseases on the surface of the body or in organs that have an anatomical relationship with the external environment, are more complex and less reliable. The first obligatory criterion of V. b. with the group of diseases under consideration, it is excreted from the affected organ. However, due to the fact that the conditionally pathogenic microbes are permanently or temporarily located in these organs in healthy people, the mere presence of a microbe in the lesion for attributing it to B. b. not enough. Therefore, as the second criterion, the population size of the intended B. is used. in the affected organ, the edges are different with acute and chronic processes, at the beginning, in the height and at the end of the disease, in cases with etiotropic therapy and without it, in autochthonous and imported microbes for the affected organ. It also depends on the competitive relationship between members of the microbiocenosis and the so-called. M-concentration of the species. At the account of all listed circumstances number of a population of a microbe, edge points to its etiol. or pathogenetic role, varies from 10 4 to 10 6 individuals. Criteria B. 6. should also include the repeated allocation of the same variant, the presence of pathogenicity factors in it, a direct correlation in the change in the number of microbial population and the clinical picture of the disease, epidemiol. data, with nosocomial infections - multiple resistance. At subacute and chronic processes important criterion of B. - increase in the titer of At to the selected microbe in the course of the disease, but in general in the specified group of diseases immunol. the criterion is less important than in pathological conditions caused by obligate pathogenic microbes.

(Source: "Glossary of Microbiology")

ACCIDENT (DISEASES); Pathogen  - English pathogen; pathogenic agent it.Anreger; Erreger; Krankheitserreger; Krankheitserreger; Pathogen French pathogène see\u003e ... Phytopathological reference dictionary

African swine fever: symptoms and pathogen  - African swine fever (lat. Pestis africana suum), African fever, East African plague, Montgomery disease - highly contagious viral swine disease, characterized by fever, skin cyanosis (cyanotic coloring) and extensive ... Encyclopedia of newsmakers

Pathogen, pathogen, husband. (specialist.). 1. The beginning, generating some sort of process. Yeast is the causative agent of fermentation. The causative agent of the disease (mainly bacteria). 2. Special electromagnetic device (radio). Explanatory Dictionary Ushakov. D.N. Ushakov. 1935 ... ... Explanatory Dictionary Ushakov

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Causative agent of infectious disease  - The causative agent of an infectious disease: a pathogenic microorganism that is evolutionarily adapted to parasitizing in the human or animal body and potentially capable of causing a disease of an infectious disease ...

Microorganisms are the most numerous inhabitants of the planet. Among them are both useful for humans, plants and animals, and pathogenic bacteria, pathogens.

Due to the introduction of such pathogenic microbes into living organisms, infectious diseases develop.

In order for causative bacteria, animals, humans to cause an infectious lesion, they must have certain properties:

• pathogenicity (the ability of pathogens to invade a living organism, multiply and provoke the development of pathologies);
• virulence (the ability of pathogens of pathology to overcome the resistance of a living organism); the higher the virulence, the smaller the number of bacteria that can cause a lesion;
• toxicity (the ability of pathogens to produce biological poison);
• contagiousness (the ability of pathogenic bacteria to be transmitted from the patient to a healthy organism).

A significant factor in the characterization of bacteria that cause infectious lesions is the degree of their resistance to external factors. To varying degrees, high and low temperatures, solar radiation and humidity levels affect the vital activity of bacteria.

For example, the ultraviolet component of sunlight is a powerful bactericidal agent. A similar effect on pathogens of infectious diseases is exerted by various chemical disinfectants (chloramine, formalin), which can quickly lead to the complete destruction of pathogenic microflora.