a biological phenomenon, the essence of which is the introduction and reproduction of microorganisms in a macroorganism with the subsequent development of various forms of their interaction from the carriage of pathogens to a pronounced disease.

Abortive infection(i. abortiva) - manifest I., characterized by a shortened acute period of the disease and the rapid disappearance of pathological phenomena.

Associated infection(i. associata) - see Mixed infection.

Autochthonous infection(nrk) - I., in which it develops in the macroorganism at the site of penetration and reproduction of the pathogen.

Generalized infection(i. generalisata) - And., in which the pathogens spread mainly through the lymphohematogenous route throughout the macroorganism.

dormant infection(i. cryptogena; .: I. cryptogenic, I. resting) - a form of manifestation of I., in which the pathogen is in an inactive state in separate foci (for example, in the palatine tonsils); It manifests itself clinically only with a sharp weakening of the body's defenses.

Infection inapparent(i. inapparens; In- + lat. appareo to appear, manifest; synonym: I. asymptomatic, I. subclinical) - a form of manifestation of I., characterized by the absence of clinical signs, cleansing the body of the pathogen and the formation of immunity.

Intercurrent infection(i. intercurrens) - exogenous I., which occurs in a patient with another infectious disease and ends earlier than it, for example, with the flu of a patient with brucellosis.

cryptogenic infection(i. cryptogena) - see Dormant infection.

The infection is latent(i. latens; synonym: I. silent, I. hidden) - a form of manifestation of I., characterized by long-term preservation of the pathogen in the body without clinical manifestations that may occur during exposure (superinfection, cooling, etc.) that cause weakening of the body.

Manifest infection(i. manifesta) - a form of manifestation of I., characterized by clearly expressed clinical signs.

No infection- see Latent infection.

Focal infection(obsolete; i. focalis; syn. I. focal) - I., in which the process is localized in a specific organ or tissue of the body; the existence of I. o. is denied, we can only speak of a local manifestation of the interaction of the pathogen with the macroorganism.

cross infection(i. cruciata) - And. as a result of the mutual exchange of pathogens among persons (sick or convalescents) who are in close contact.

Resting infection- see Dormant infection.

The infection is latent(i. latens) - see Latent infection.

Mixed infection(i. mixta; synonym: I. associated, I. combined) - I. with the participation of two or more different pathogens (usually viruses); is manifested by the predominance of the clinical picture of the disease caused by one of them, or by an atypical, more severe course.

Combined infection(i. mixta) - see Mixed infection.

Erased infection- a form of manifestation of I., characterized by a weak severity of clinical manifestations.

subclinical infection(i. subclinicalis) - see Inapparant infection.

Focal infection(i. focalis - obsolete) - see Focal infection.

chronic infection(i. chronica) - a form of manifestation of I., characterized by a long course.

The infection is exogenous(i. exogena) - And., in which pathogens are introduced from the outside, usually through environmental factors; the term covers all forms And., except an autoinfection.

Experimental infection(i. experimentalis) - I., artificially reproduced in laboratory animals by dosed infection with known pathogens.

an integral part of a number of terms-phrases (often in the plural) denoting groups of infectious diseases identified by epidemiological or clinical signs, and sometimes a separate infectious disease; This use of the term “infection is traditionally common, but raises objections, since the concepts denoted with its help, in essence, represent one of the manifestations of I. as a biological phenomenon.

hospital infections

Viral infections(i. virales) - infectious diseases caused by viruses.

nosocomial infections(i. nosocomiales; synonym: I. hospital, I. in-hospital, I. hospital, I. nosocomial) -

1) infectious diseases that have joined the underlying disease or injury while the patient (injured) is in the hospital;

2) infectious diseases in medical workers that have arisen as a result of infection in the treatment or care of infectious patients.

Hospital-acquired infections- see Nosocomial infections.

Airborne infections- see Respiratory tract infections.

herpetic infection(i. herpetica) - an infectious disease caused by viruses of the herpes group; include simple and herpes zoster, chicken pox, cytomegaly, etc. to I. g.

hospital infections- see Nosocomial infections.

Children's infections(i. infantum) - infectious diseases occurring mainly in children.

Respiratory tract infections(syn. I. airborne) - infectious diseases, the pathogens of which are localized mainly in the mucous membranes of the respiratory tract, and infection occurs mainly through the airborne transmission mechanism; include, sore throat, meningococcal infection, etc.

quarantine infections(syn. I. convention) - infectious diseases that are covered by the "International Health Regulations"; include plague, cholera, smallpox, and yellow fever.

Intestinal infections- infectious diseases, the causative agents of which are localized mainly in the intestine, and infection occurs mainly through the fecal-oral transmission mechanism; include dysentery, cholera, etc.

Coxsackie infections- infectious diseases caused by enteroviruses from the Coxsackie group; include herpangina, epidemic pleurodynia, neonatal encephalomyocarditis, some viral diarrheas, and others.

Conventional infections- see quarantine infections.

Blood infections- infectious diseases, the causative agents of which are localized mainly in the blood and lymph, and infection occurs mainly through a transmissible transmission mechanism; include, relapsing fever, tick and mosquito fevers, etc.

Infections are slow- little studied infectious diseases of humans and animals caused by viruses, characterized by a long (sometimes many years) incubation period, with the persistence and accumulation of the pathogen in the macroorganism, a progressive prolonged course, mainly with the phenomena of a degenerative process in the central nervous system; to I. m. include, scrapie, (with intrauterine infection), etc.

meningococcal infection(i. meningococciea) - an acute infectious disease caused by meningitidis with airborne transmission, characterized by damage to the nasopharynx (, carriage), as well as generalization in the form of meningococcemia or meningitis.

Infections of the outer integument- infectious diseases, infection by pathogens of which occurs mainly through the contact mechanism of infection transmission; include, rabies, trachoma, etc.

Nosocomial infections(Latin nosocomialis hospital) - see Nosocomial infections.

Infections are especially dangerous- infectious diseases characterized by very rapid spread, severe course, long-term subsequent disability or high mortality; include plague, cholera, and smallpox.

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Chapter 1. Infection, infectious process, infectious disease

Infectious diseases are widespread throughout the world, caused by various microorganisms. "Contagious" diseases have been known since ancient times, information about them can be found in the oldest written monuments: in the Indian Vedas, the works of Ancient China and Ancient Egypt. Descriptions of some infectious diseases, such as dysentery, tetanus, erysipelas, anthrax, viral hepatitis, etc., can be found in the writings of Hippocrates (460-377 BC). In the Russian chronicles, infections were described under the name of epidemics, epidemic plagues, emphasizing the main feature - mass character, high mortality and rapid prevalence among the population. Devastating epidemics and pandemics of infectious diseases have been described. It is known that in the Middle Ages an epidemic of plague (“black death”) raged, from which a third of the population of Europe died out, and all over the world from the plague in the XIV century. more than 50 million people died. During World War I, there was an influenza pandemic (“Spanish flu”) that affected 500 million people, 20 million of them died. For a long time, nothing was known about the cause of infectious diseases, it was believed that these diseases arise in connection with "miasms" - poisonous air fumes. This teaching is in the 16th century. was replaced by the doctrine of "contagia" (Fraxtoro). In the XVII-XIX centuries. many childhood infections have been described, such as measles, chicken pox, scarlet fever, etc. The full flowering of the doctrine of infectious diseases occurred in the 19th century. during the period of rapid development of microbiology and the emergence of immunology in the twentieth century. (L. Pasteur, R. Koch, I. I. Mechnikov, L. Erlich, G. N. Minkh, D. K. Zabolotny, L. A. Zilber). Advances and achievements in microbiology contributed to the isolation of infectious diseases as an independent science and the further development of the teachings on the etiology, pathogenesis, symptoms, treatment and prevention of infectious diseases. A contribution to the development of childhood infections was made by the works of A. A. Koltypin, M. G. Danilevich, D. D. Lebedev, M. S. Maslov, S. D. Nosov and other scientists.

Infectious diseases are a large group of human diseases resulting from exposure to the body of viruses, bacteria and protozoa. They develop during the interaction of two independent biosystems - a macroorganism and a microorganism under the influence of the external environment, and each of them has its own specific biological activity.

Infection is the interaction of a macroorganism with a microorganism under certain conditions of the external and social environment, as a result of which pathological, protective, adaptive, compensatory reactions develop, which are combined into an infectious process. The infectious process is the essence of an infectious disease and can manifest itself at all levels of biosystem organization - submolecular, subcellular, cellular, tissue, organ, organism.

However, not every exposure of the pathogen to the body causes disease. An infectious disease occurs if there is a violation of the function of the body and the appearance of a clinical picture. Thus, an infectious disease is an extreme degree of development of an infectious process. If, when the pathogen enters the body, no clinical picture is formed, then they speak of a healthy carriage, which can be in children with residual specific immunity or in people with congenital natural immunity. There is also convalescent carriage that occurs during the period of recovery from an infectious disease. Depending on the conditions of infection, the properties of the infectious agent, the state of the macroorganism (susceptibility, the degree of specific and nonspecific reactivity), several forms of interaction of the microorganism with the human body are described.

Manifest forms (manifested clinically) are divided into acute and chronic. There are also typical, atypical and fulminant forms, mostly ending in death. According to severity, they are divided into mild, moderate and severe forms.

In the acute form of a clinically manifested infection, the pathogen stays in the body for a short time. This form is characterized by a high intensity of release of pathogens into the environment by patients, which creates a high infectivity of patients. Many infectious diseases are acute, such as plague, smallpox, scarlet fever. Others, both acute and chronic - brucellosis, hepatitis B, dysentery.

The chronic form of the disease is characterized by a longer stay of the pathogen in the body, frequent exacerbations and remissions of the pathological process and, in case of timely treatment, a favorable outcome and recovery, as in the acute form.

Re-infection due to infection with the same infectious agent is called reinfection. If infection with another infectious agent occurs before recovery from the disease, then they speak of superinfection.

Bacteriocarrier is a process that is asymptomatic in acute or chronic form. Pathogens are present in the body, but the manifestation of the process does not occur, and outwardly the person remains healthy. Immunological changes are revealed in the body, as well as functional morphological disorders in organs and tissues, typical for this disease.

The subclinical form of infection is of great epidemiological importance, since such patients are a reservoir and source of pathogens while maintaining their ability to work and social activity, which complicates the epidemic situation. However, the high frequency of subclinical forms of certain infections (dysentery, meningococcal infection, influenza, etc.) contributes to the formation of a massive immune layer among people, which to a certain extent stops the spread of these infectious diseases.

Perelatent (latent) infection occurs as a result of prolonged asymptomatic interaction of a macroorganism with a microorganism. At its core, it is a chronic infectious disease with a benign course, occurs in diseases such as hepatitis B, herpes infection, typhoid fever, cytomegalovirus infection, and many others. etc. This form is more common in children with reduced cellular and humoral immunity, while the infectious agent is either in a defective state, or in a special stage of its life (L - form). The formation of L - forms occurs under the influence of the protective immune forces of the body and drugs (antibiotics). Atypical strains are formed with a change in all properties of the microorganism.

An essentially new form of infection interaction with the human body is a slow infection. It is characterized by a long (up to several years) incubation period - a stage at which there is no disease. At the same time, the disease progresses steadily with the development of severe disorders in many organs and systems (most often in the nervous system), and death is often observed. This type of infection includes: AIDS, congenital rubella, chronic active hepatitis with the transition to cirrhosis, etc.

Infectious diseases resulting from infection by microorganisms of the same species are called monoinfections. When infected with bacteria of different types - mixed, or mixed infection. One of the options for a mixed infection is a secondary infection, in which a new one joins an already existing disease.

The infectious process can occur due to the activation of saprophytic microflora, i.e. those microbes that constantly live on the skin and mucous membranes. In these cases, we speak of endogenous, or autoinfection, which most often occurs in debilitated children with chronic diseases, in children who have received antibacterial or cytostatic (suppressive immunity) therapy for a long time.

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Part I. Infectious diseases. basic conceptsChapter 2

Definitions of the concepts "infection", "infectious process", "infectious disease" The term "Infection" (lat. Infectio - infection) is a set of biological processes occurring in a macroorganism when pathogenic microorganisms are introduced into it, regardless of whether this introduction for is the development of an overt or latent pathological process, or it will be limited only to temporary carriage or long-term persistence of the pathogen.

The infectious process is a complex of adaptive reactions of a macroorganism that develops in response to the introduction and reproduction of a pathogenic microorganism in it and is aimed at restoring homeostasis and disturbed biological balance with the environment. The infectious process occurs when there are three components: - pathogen, - susceptible microorganism (patient), - factor of infection transmission from an infected organism to a healthy one. Infectious disease - An infectious disease is a violation of the normal functioning of the body, due to the introduction and reproduction of pathogenic microorganisms in it. An infectious disease can be defined as a special case of an infectious process.

The place of penetration of the pathogen is called the entrance gate of infection - tissues deprived of physiological protection against a particular type of microorganisms serve as a place for its penetration into the macroorganism. Cylindrical epithelium for gonococci. Staphylococci, streptococci can penetrate in several ways Ways of penetration of the pathogen into the macroorganism: - through the mucous membrane (overcoming natural defense factors, microorganisms attach to epithelial cells and colonize it; then penetrate into the lymphatic system, blood, tissues of internal organs, microorganisms attach to epithelial cells and colonize it) - through microtraumas of the skin (the pathogen, bypassing the natural barriers of the skin and mucous membranes, penetrates into the lymphatic system and into the blood)

Properties of pathogens: Pathogenicity (pathogenicity) is a specific multifactorial trait that characterizes the potential ability of a microbe to cause an infectious process. Invasiveness - the ability of the pathogen to penetrate through the skin and mucous membranes into the internal environment of the macroorganism, with subsequent possible spread through organs and tissues Toxigenicity - this is the ability of microbes to produce toxins

To determine the degree of pathogenicity, the concept is used as - virulence, which is an individual sign of any pathogenic strain. Degrees of virulence of the microorganism Depending on the degree of manifestation of this trait, all strains can be divided into high-, moderate-, low-virulence. The higher the virulence of the strain, the lower should be the infectious dose, which is the number of viable microbes that can cause the development of an infectious process in the host organism. The infectious dose of the pathogen is the minimum number of microbial cells that can cause an infectious process. The value of the infectious dose depends on the virulent properties of the pathogen. The higher the virulence, the lower the infectious dose. For the highly virulent pathogen Yersinia pestis (plague), a few bacterial cells of Shigella dysenteriae are enough - dozens of cells

Properties of the macroorganism 1. Susceptibility to a particular pathogen. 2. Resistance - a state of resistance, which is determined by factors of non-specific protection. Susceptibility - the ability of a macroorganism to respond to infection by the development of an infectious process. Susceptibility can be specific and individual. Species susceptibility is inherent in a given species of animal or person. It is genetically determined. A certain type of microbe finds the optimal environment for its existence in the tissues of a certain type of host.

Individual susceptibility is determined by the state of each particular organism. It depends on many factors: 1) the quality and quantity of the pathogen; quality - the severity of the invasive and aggressive properties of the pathogen, quantity - the infectious dose - a certain critical dose, below which the disease may not develop (for cholera, it is necessary to administer V. cholerae in a dose by oral route); 2) entry gate - a tissue or organ through which the pathogen enters the macroorganism; for most pathogens, penetration through certain entrance gates is necessary for the development of the disease (for gonococcus - only through the mucous membranes of the genital organs or the conjunctiva of the eye, for the causative agent of dysentery - through the mucous membrane of the colon, for the influenza virus - through the mucous membrane of the respiratory tract); there are microorganisms that can penetrate through any entrance gate (the causative agent of the plague, staphylococci).

3) general physiological reactivity of the organism; it is determined by the physiological characteristics of the macroorganism, the nature of metabolism, the function of internal organs, endocrine glands, and the characteristics of immunity. The general physiological reactivity is affected by: a) gender and age: there are childhood infections (scarlet fever, whooping cough, measles, parotitis), pneumonia is severe in old age, during pregnancy women are more susceptible to staphylococcal and streptococcal infections, up to 6 months children are resistant to many infections, tk. receive antibodies from the mother; b) the state of the nervous system: depression of the nervous system contributes to a more severe course of infection; mental disorders reduce the regulatory function of the central nervous system; c) the presence of somatic diseases (diabetes, diseases of the cardiovascular system, liver, kidneys);

D) the state of normal microflora, whose representatives have antagonistic properties; e) nutrition: with insufficient and malnutrition, people are more likely to be susceptible to infectious diseases (tuberculosis, dysentery, cholera), while protein components of food, vitamins and trace elements are of the greatest importance (necessary for the synthesis of antibodies and maintaining active phagocytosis) as a result of starvation, there may be lost not only individual, but also species immunity; lack of vitamins leads to metabolic disorders, which reduces resistance to infections; f) immunobiological features of the organism, i.e. stability of natural protective factors.

Influence of environmental factors on the course of the infectious process. Environmental factors affect both the microorganism, its resistance and persistence in the external environment, and the resistance of the macroorganism. Refrigeration reduces resistance to many pathogenic and opportunistic microbes. For example, the effect of cold and humid air reduces the resistance of the mucous membrane of the respiratory tract, which leads to acute respiratory diseases in the autumn-winter period. Overheating reduces immunity. Air pollution leads to an increase in upper respiratory diseases in big cities. Solar radiation greatly increases resistance, but in some cases, prolonged and intense radiation reduces resistance (malaria relapses in people exposed to intense solar radiation). Ionizing radiation in large doses makes the body defenseless against infection, disrupting the permeability of the mucous membranes, sharply reducing the function of the lymphoid tissue and the protective properties of the blood. Social conditions: normal conditions of work, life, rest, sports increase the body's resistance; poor sanitary and hygienic conditions, physical and mental fatigue cause a weakening of the body's defenses.

Forms of the infectious process. BY NATURE OF THE PATHOGENS: bacterial, viral, fungal, protozoal. BY ORIGIN: - exogenous - infection from the environment with food, water, soil, air, secretions of a sick person; - endogenous - infection with opportunistic microorganisms that live in the body of the person himself, which occurs with a decrease in immunity; - autoinfection - self-infection by transfer (usually by the hands of the patient) from one place to another (from the mouth or nose to the wound surface).

BY THE NUMBER OF PATHOGENS: - monoinfection - one species; - mixed - two or more types of pathogens. BY DURATION: - acute - short-term (from one week to a month); - chronic - protracted course (several months - several years); long stay - persistence.

BY LOCALIZATION: - focal - localized in the local focus; - generalized - the pathogen spreads through the body with blood (hematogenous route) or with lymph (lymphogenic route). Focal can go into generalized. Secondary infection - infection with another type of pathogen during the main disease (complication of the main disease by another microbe) - measles is complicated by pneumonia. Relapse - the return of symptoms due to pathogens remaining in the body (relapsing fever, malaria). Reinfection is re-infection with the same species after recovery. Superinfection - infection with the same species during the disease (before recovery).

Features of infectious diseases Contagiousness (infectiousness) - the ability of the causative agent of an infectious disease to be transmitted from an infected organism to a healthy one. Specificity - each pathogenic microorganism causes a disease characterized by a certain localization of the process and the nature of the lesion. Cyclicity - a change in periods of the disease, strictly following each other: incubation period - prodromal period - the height of the disease - convalescence

The value of specific immunity Formation of specific immunity - in the process of development of the infectious process, specific immunity is formed, the intensity and duration of which can vary from several months to several years and even decades

2. Prodrome (prodrome) is a manifestation of common symptoms - discomfort, fatigue, chills. Clinically, it is intoxication. Localization of the pathogen - penetrates into the blood, lymph, secretion of toxins occurs, the activity of innate immunity factors is manifested

Classification of infectious diseases Intestinal infections Respiratory tract infections Blood infections Zoonotic infections Contact - household infections The causative agent is excreted in feces or urine. Transmission factors: food, water, flies, dirty hands, household items. Infection through the mouth. Transmission by airborne droplets or airborne dust The pathogen is transmitted through insect bites Diseases transmitted through animal bites Transmitted by contact with a sick person

Group of infectious diseases Infections included in the group Intestinal infections Typhoid fever, paratyphoid fever A and B, dysentery, cholera, food poisoning, etc. Respiratory tract infections, or airborne infections Influenza, measles, diphtheria, scarlet fever, smallpox, tonsillitis, tuberculosis Blood infections Sypsis and relapsing fever, malaria, plague, tularemia, tick-borne encephalitis, AIDS Zoonotic infections Rabies Contact-household Infectious skin and venereal diseases, sexually transmitted (syphilis, gonorrhea, chlamydia, etc.)

Ways of spread of infections Fecal-oral This way all intestinal infections are transmitted. The microbe with the feces, vomit of the patient gets on food, water, dishes, and then through the mouth into the gastrointestinal tract of a healthy person. Fecal-oral All intestinal infections are transmitted in this way. The microbe with feces, vomit of the patient gets on food, water, dishes, and then through the mouth into the gastrointestinal tract of a healthy person. Liquid Characteristic for blood infections. Carriers of this group of diseases are blood-sucking insects: fleas, lice, ticks, mosquitoes, etc. Liquid Characteristic for blood infections. Carriers of this group of diseases are blood-sucking insects: fleas, lice, ticks, mosquitoes, etc. Contact or household contact This way most venereal diseases are transmitted through close contact between a healthy person and a sick person Contact or household contact This way most venereal diseases are transmitted through close contact between a healthy person and a sick person Infection occurs through bites or close contact with sick animals. Zoonotic Carriers of zoonotic infections are wild and domestic animals. Infection occurs through bites or close contact with sick animals. Airborne This way all viral diseases of the upper respiratory tract spread. The virus with mucus, when sneezing or talking, enters the mucous membranes of the upper respiratory tract of a healthy person. Airborne This way all viral diseases of the upper respiratory tract spread. The virus with mucus, when sneezing or talking, enters the mucous membranes of the upper respiratory tract of a healthy person. The main ways of transmission of infection and their characteristics

Epidemiology is a science that studies the conditions for the occurrence and mechanisms of the spread of the epidemic process. The epidemiological process is a chain of continuous, one after another infectious conditions (from asymptomatic carriage to a manifest disease) as a result of the circulation of the pathogen in the team.

The epidemic process is the emergence and spread among the population of specific infectious conditions, from asymptomatic carriers to manifest diseases caused by the circulation of the pathogen in the team. The manifest form of the disease is the clinical form of the disease with a full set of symptoms characteristic of it. The asymptomatic form is hidden.

1. Source of infection - a living or abiotic object, which is a place of natural activity of pathogenic microbes, due to which people and animals are infected. The source of infection can be a human and animal organism, abiotic objects of the environment (water, food).

Source of the causative agent of infection Source of the causative agent of infection - a diseased organism - bacteria carriers in which the pathogen not only persists, multiplies, but is also released into the external environment or directly transmitted to another susceptible organism An organism that does not show signs of disease. They represent a great danger to others, since it is much more difficult to identify them than patients. An organism that does not show signs of disease. They represent a great danger to others, since it is much more difficult to identify them than patients.

2. Mechanism of transmission - a way of moving infectious agents and invasive diseases from an infected organism to a susceptible one. Includes 3 phases: a) removal of the pathogen from the host organism into the environment; b) the presence of the pathogen in environmental objects (biotic and abiotic); c) the introduction of the pathogen into a susceptible organism. Transmission mechanisms are distinguished: fecal-oral, aerogenic, transmissible, contact

Transmission factors are elements of the environment that ensure the transfer of microbes from one organism to another. Ways of transmission - an element of the external environment, ensuring the entry of the pathogen from one organism to another, under certain external conditions. For the fecal-oral mechanism, there are ways: alimentary (food), water and contact-household. For the aerogenic mechanism, there are ways: air-droplet and air-dust.

3. Susceptible collective, if the immune layer in the population is 95% or more, then in this collective the state of epidemic well-being is achieved. Therefore, the task of preventing epidemics is to create an immune layer in the collectives through vaccination.

Prevention of infectious diseases is a set of measures aimed at ensuring a high level of people's health, their creative longevity, eliminating the causes of diseases, improving working conditions, living and recreation of the population, and protecting the environment.

Anti-epidemic (anti-epizootic) and sanitary and hygienic measures early detection of patients and those suspicious of the disease by going around the yards; enhanced medical and veterinary surveillance of those infected, their isolation and treatment; sanitary treatment of people with disinfection of clothes, shoes, care items, etc.; disinfection of the territory, structures, transport, residential and public premises; establishment of an anti-epidemic regime for the operation of medical and preventive and other medical institutions; disinfection of food waste, sewage and waste products of sick and healthy individuals; carrying out sanitary and educational work

3 degrees of intensity of the epidemic process: I - Sporadic incidence - the incidence of a given nosological form in a given territory in a certain historical period of time; II - Epidemic - the level of incidence of a given nosological form in a certain area in a specific period of time, sharply exceeding the level of sporadic incidence; III - Pandemic level, sharply exceeding the epidemic. The pandemic is spreading very quickly, capturing a country, a continent, the whole world. An epidemic smaller than a pandemic covers a city, region, country.

Quarantine (conventional) diseases are the most dangerous diseases prone to rapid spread. Hospital (nosocomial) infections - diseases that occur in weakened individuals who become infected in hospital conditions (suppuration of postoperative wounds, pneumonia, sepsis). The fight against epidemics is aimed at all 3 links of the epidemic process. But with each disease, the emphasis is on the most important link (for intestinal infections - interruption of transmission routes; for airborne infections - the creation of collective immunity).

Especially dangerous (OOI), as they cause severe complications in the human body and can even cause death. Such infections should be kept under public health control, providing a number of measures that would prevent the spread of these diseases. A set of such measures is called quarantine, and infections that are subject to special medical and sanitary attention are called quarantine. The list of quarantine diseases has changed over time. Some of them could be overcome by vaccination, others remained dangerous. Currently, it is customary to call quarantine only a group of especially dangerous infections (DOI): - yellow fever - plague - smallpox - cholera