The essence and characteristics of an infectious disease. General features of infectious diseases A distinctive feature of infectious diseases is
An infectious disease is a specific infectious condition caused by the introduction of pathogenic microbes and/or their toxins into the macroorganism, which interact with the cells and tissues of the macroorganism.
Features of the infectious process
1. The pathogen itself, that is, each m/o has its own disease.
2. Specificity , which lies in the fact that each pathogenic microbe causes its own, unique infectious disease and is localized in a particular organ or tissue.
3. Contagiousness (from lat. contaggiosus - contagious, contagious) refers to the ease with which a pathogen is transmitted from an infected organism to an uninfected one, or the rapidity with which germs spread among a susceptible population by chain reaction or fan-shaped transmission.
Infectious diseases are characterized by the presence infectious period- the period of time during an infectious disease when the pathogen can spread directly or indirectly from a sick macroorganism to a susceptible macroorganism, including with the participation of arthropod vectors. The duration and nature of this period are specific to the disease.
For qualitative assessment of the degree of contagiousness, infectiousness index, defined as the percentage of people exposed to the disease over a certain period of time.
4. Cyclicity of the flow, which consists in the presence of successively changing periods based on the pathogenesis of the disease. The duration of the periods depends both on the properties of the microbe and on the resistance of the macroorganism, and the characteristics of immunogenesis. Even with the same disease, the duration of these periods may vary among different individuals.
The following periods of disease development are distinguished: incubation (latent); prodromal (initial); the period of the main or pronounced clinical manifestations of the disease (the height of the disease); period of extinction of symptoms of the disease (early period of convalescence); period of recovery (reconvalescence).
The period from the moment of introduction of the microbe (infection, infection) into the macroorganism until the onset of the first clinical manifestations of the disease is called incubation(from lat. incubo - rest or incubation - without external manifestations, hidden). During the incubation period, the pathogen adapts to the internal environment of the infected macroorganism and overcomes the latter’s defense mechanisms. In addition to the adaptation of microbes, they multiply and accumulate in the macroorganism, move and selectively accumulate in certain organs and tissues (tissue and organ tropism), which are most susceptible to damage. On the part of the macroorganism, already in the incubation period, the mobilization of its protective forces occurs. There are no signs of the disease in this period yet, but with special studies it is possible to detect the initial manifestations of the pathological process in the form of characteristic morphological changes, metabolic and immunological changes, the circulation of microbes and their antigens in the blood. From an epidemiological perspective, it is important that a macroorganism at the end of the incubation period can pose an epidemiological danger due to the release of microbes from it into the environment.
Prodromal or initial period(from Greek prodromes - precursor) begins with the appearance of the first clinical symptoms of a general disease as a result of intoxication of the macroorganism (malaise, chills, fever, headache, nausea, etc.). There are no characteristic specific clinical symptoms on the basis of which an accurate clinical diagnosis could be made during this period. An inflammatory focus often appears at the site of the entrance gate of infection - primary affect. If regional lymph nodes are involved in the process, then they talk about primary complex.
The prodromal period is not observed in all infectious diseases. It usually lasts 1-2 days, but can be shortened to several hours or extended to 5-10 days or more.
The prodromal period gives way perihome of the main or pronounced clinicalmanifestations of the disease(the height of the period), which is characterized by the maximum severity of general nonspecific symptoms of the disease and the appearance of specific or absolute (obligate, decisive, pathognomonic), characteristic only of this infection, symptoms of the disease, which make it possible to make an accurate clinical diagnosis. It is during this period that the specific pathogenic properties of microbes and the response of the macroorganism find their fullest expression. This period is often divided into three stages: 1) the stage of increasing clinical manifestations (stadium incrementi); 2) stage of maximum severity of clinical manifestations (stadium fastigii); 3) stage of weakening of clinical manifestations (stadium decrementi). The duration of this period varies significantly for different infectious diseases, as well as for the same disease in different individuals (from several hours to several days and even months). This period may end fatally, or the disease progresses to the next period, which is called period of symptoms fadingillness (early period of convalescence).
During the period of extinction, the main symptoms of the disease disappear and the temperature normalizes. This period is replaced period of convalescence(from lat. re - denoting repetition of action and convalescentia - recovery), which is characterized by the absence of clinical symptoms, restoration of the structure and function of organs, cessation of the proliferation of the pathogen in the macroorganism and the death of the microbe, or the process can become a microbial carrier. The duration of the convalescence period also varies widely even for the same disease and depends on its form, severity, immunological characteristics of the macroorganism, and the effectiveness of the treatment.
Recovery can be complete, when all impaired functions are restored, or incomplete, when residual (residual) phenomena remain, which are more or less stable changes in tissues and organs that arise at the site of development of the pathological process (deformations and scars, paralysis, tissue atrophy, etc.) .d.). There are: a) clinical recovery, in which only the visible clinical symptoms of the disease disappear; b) microbiological recovery, accompanied by the release of the macroorganism from the microbe; c) morphological recovery, accompanied by restoration of the morphological and physiological properties of the affected tissues and organs. Typically, clinical and microbiological recovery do not coincide with complete restoration of morphological damage that lasts for a long time. In addition to complete recovery, the outcome of an infectious disease can be the formation of microbial carriage, transition to a chronic form of the disease, or death.
5. Formation of immunity, which is a characteristic feature of the infectious process. The intensity and duration of acquired immunity vary significantly in different infectious diseases - from pronounced and persistent, practically excluding the possibility of re-infection throughout life (for example, with measles, plague, smallpox, etc.) to weak and short-term, causing the possibility of re-infection diseases even after a short period of time (for example, with shigellosis). With most infectious diseases, a stable, intense immunity is formed.
The intensity of the formation of immunity during an infectious disease largely determines the characteristics of the course and outcome of the infectious disease. Characteristic featurethe pathogenesis of infectious diseases isdevelopment of secondary immunodeficiency. In some cases, an inadequately expressed immune reaction aimed at localizing and eliminating the microbe takes on an immunopathological character (hyperergic reactions), which contributes to the transition of the infectious process into a chronic form and can put the macroorganism on the brink of death. With a low level of immunity and the presence of microbes in the macroorganism, exacerbations and relapses may occur. Exacerbation- this is an increase in the symptoms of the disease during the period of extinction or the period of convalescence, and relapse- is the occurrence of repeated attacks of the disease during the recovery period after the disappearance of clinical symptoms of the disease. Exacerbations and relapses are observed mainly in long-term infectious diseases, for example, typhoid fever, erysipelas, brucellosis, tuberculosis, etc. They arise under the influence of factors that reduce the resistance of the macroorganism, and can be associated with the natural cycle of development of microbes in the macroorganism, such as for example, with malaria or relapsing fever. Exacerbations and relapses can be both clinical and laboratory.
6. To make a diagnosis of infectious diseases, they are used specificmicrobiological and immunological methodsdiagnostics(microscopic, bacteriological, virological and serological studies, as well as bioassay and skin allergy tests), which are often the only reliable way to confirm the diagnosis. These methods are divided into basic And auxiliary(additional), as well as methods express diagnostics.
7. Application specific drugs, directed directly against a given microbe and its toxins. Specific drugs include vaccines, serums and immunoglobulins, bacteriophages, eubiotics and immunomodulators.
8. Possibility of developing microbial carriage.
The generally accepted term “infectious diseases” was introduced by the German physician Christoph Wilhelm Hufeland. Main signs of infectious diseases:
* the presence of a specific pathogen as the direct cause of the disease;
* contagiousness (infectiousness) or the occurrence of several (many) cases of diseases caused by a common source of infection (zoonoses, sapronoses);
* often prone to widespread epidemic spread;
* cyclical course (consecutive change of periods of illness);
* the possibility of developing exacerbations and relapses, protracted and chronic forms;
* development of immune reactions to the Ag (antigen) of the pathogen;
* the possibility of developing carriage of the pathogen.
Specificity. Each infectious disease is caused by a specific pathogen. Specific pathogens of infectious diseases can be bacteria, rickettsia, chlamydia, mycoplasma, fungi, viruses, and prions. However, infections (for example, purulent-inflammatory processes) caused by various microbes are known.
A cyclical course is characteristic of most infectious diseases. It is expressed in the sequential change of certain periods of the disease - incubation (latent), prodromal (initial), the period of main manifestations (the height of the disease), the extinction of symptoms (early convalescence) and recovery (convalescence).
Incubation period is the period from the moment of infection to the appearance of the first signs of the disease. During this period, the body actively reproduces and accumulates the pathogen and its toxins up to a certain threshold amount, after which the body begins to respond with certain clinical manifestations, i.e., the next, prodromal period begins. The duration of the incubation period varies on average from several days to several weeks, but it can be equal to several hours and last several months, and in case of leprosy - several years. This depends on a number of reasons - the magnitude of the infectious dose and the degree of pathogenicity of the pathogen, as well as on the state of resistance of the organism.
Prodromal period, or period of precursors. It is usually characterized by nonspecific, general manifestations - weakness, fatigue, headache, general malaise, fever, etc. Its duration varies between 24 - 48 hours.
The period of development (heyday) of the disease. It is also often characterized by a certain cyclicity. There is a stage of increasing symptoms (incrementum stage), flourishing of the disease (aste stage) and a period of fading of symptoms (decrementum stage). In the typical form of the disease, this period is characterized by the manifestation of symptoms specific to the disease, as well as some general symptoms, in particular, fever, intoxication, inflammation, and sometimes the appearance of a rash.
Outcome period. During this period the following may occur:
· Relapse of the disease - the return of the clinical manifestations of the disease without re-infection, due to the pathogens remaining in the body;
· Superinfection - infection of a macroorganism with the same pathogen before recovery. If this happens after recovery, then it is called reinfection, because. it occurs as a result of a new infection with the same pathogen, as often happens with influenza, dysentery, and gonorrhea.
· Bacterial carriage, carriage of the causative agent of any infectious disease without clinical manifestations;
· Recovery, or convalescence. Clinical recovery usually occurs earlier than pathological and bacteriological recovery. The person is practically healthy, but some pathoanatomical changes still remain at the site of the localization of the process (for example, after suffering from dysentery on the mucous membrane of the colon). Convalescence can be complete: all processes end completely without any aggravating consequences. However, some diseases leave serious consequences, for example, muscle paralysis after polio, encephalitis; cirrhosis of the liver after viral hepatitis B, etc. Particular attention should be paid to bacteriological recovery after an infectious disease, i.e. complete liberation of the body from the pathogen. For various infectious diseases, the period of bacteriological recovery varies, and this is taken into account when discharging such patients from the hospital. For example, with typhoid fever, up to 80% of convalescents during the first two weeks are bacteria carriers.
· Death. It must be remembered that the corpses of infectious patients are subject to mandatory disinfection, because pose a certain epidemiological danger due to the high content of microbial agents in them.
2. Contagiousness– infectiousness, the ability of a pathogen to cause disease
(the ability of transmission from an infected organism to an uninfected one), or the speed and intensity of infection. Contagiousness index is the percentage of sick people who were exposed to the risk of infection at a certain point in time.
3. Cyclicity- sequential change of periods of the disease. Sometimes, against the background of complete clinical recovery, a person continues to release microorganisms into the environment - microbial carriers or carriage. It is divided into:
Ø Acute - up to 3 months.
Ø Protracted – up to 6 months
Ø Chronic – more than 6 months
Routes of infection.
Infection with microorganisms can occur through damaged skin and mucous membranes (eye tissue, respiratory tract, genitourinary tract). Infection through intact skin is quite difficult, since the skin is a powerful barrier. But even the most insignificant injuries (insect bite, needle prick) can cause infection. If the entry gate for infection is the mucous membranes, then 3 mechanisms of pathogenesis are possible:
1. Reproduction of the pathogen on the surface of the epithelium.
2. Penetration of the pathogen into cells, followed by intracellular digestion and reproduction.
3. Penetration of the pathogen into the bloodstream and spread throughout the body.
Methods of infection.
The location of the entrance gate depends on the method of infection, which is important. For example, the plague!!! If infection occurs through a flea bite - crushing the flea and subsequent scratching (contaminative), then the cutaneous bubonic form occurs. If
When infection occurs by airborne droplets, the most severe form of plague develops – pneumonic. For pathogens of intestinal infections, the predominant transmission mechanism is fecal-oral, and the route of transmission is nutritional. For respiratory diseases, the transmission mechanism is aerogenic, and the route is airborne.
The blood of a healthy person and animal is sterile, as it has strong antimicrobial properties due to the presence of humoral immunity factors (complement system), as well as cellular immunity factors (lymphocyte corporation).
But when an infectious process occurs, the causative agent of the disease or its metabolic products - toxins - appear in the blood and circulate for some time. It is through the blood that the infection spreads throughout the body - generalization of the process. The appearance of pathogens or toxins, i.e. foreign agents in large quantities in the blood are accompanied by fever, which is regarded as a protective reaction (the release of antibodies - immunoglobulins and other substances that trigger the body's immune response).
Ø Antigenemia is the circulation of foreign antigens or autoantigens in the blood and the release of antibodies to them. Circulating immune complexes are formed (CIC = Ag + Ab). These complexes are detected in the body using serological reactions.
Ø Bacteremia is the circulation of bacteria in the blood. It occurs as a result of the penetration of the pathogen into the blood through the natural barriers of the body, as well as during vector-borne infections after the bite of arthropods (typhoid fever, relapsing fever, plague, tularemia) Bacteremia is an obligatory stage in the pathogenesis of the disease. It ensures the transmission of the pathogen to another host, preserving it as a species. Bacteremia can be caused by surgical interventions, trauma, radiation sickness, malignant tumors, and various severe forms of diseases caused by opportunistic bacteria.
Unlike sepsis and septicopyemia, with bacteremia, bacteria in the blood only circulate, but do not multiply. Bacteremia is a symptom of the disease and one of its stages. The diagnosis of bacteremia is made by isolating a culture of the pathogen or by infection through the blood of a sick laboratory animal.
Ø Viremia is the circulation of viruses in the blood.
Ø Sepsis or rotten blood is a severe generalized acute or chronic febrile disease of a person, caused by continuous or periodic entry of a pathogen into the blood from a focus of purulent inflammation. Sepsis is characterized by a discrepancy between severe general disorders and local changes and the frequent formation of new foci of purulent inflammation in various organs and tissues. Unlike bacteremia in sepsis, due to a decrease in the bactericidal properties of the blood, the pathogen multiplies in the circulatory and lymphatic systems. Sepsis is a consequence of the generalization of localized purulent foci. The etiology of sepsis is varied; common pathogens are staphylococci, streptococci, Gr(-) bacteria from the Enterobacteriaceae family, meningococci, opportunistic bacteria, and fungi.
Depending on the location of the primary focus and the entrance gate of the pathogen, they are distinguished: postpartum, post-abortion, peritoneal, wound, burn, oral, urosepsis, neonatal (infection can occur during labor and in fetal development), cryptogenic (the primary focus of purulent inflammation remains unrecognized ) and another.
Ø Septicopyemia is a form of sepsis in which, along with intoxication of the body, the formation of purulent metastatic foci occurs in various tissues and organs, combined with the presence and reproduction of the pathogen in the circulatory and lymphatic systems.
Ø Toxinemia is the circulation of bacterial exotoxins in the blood. The pathogen itself is absent in the blood, but the target cells are affected by the products of its vital activity. Botulism, diphtheria are exotoxins, and tetanus is an anaerobic infection.
Ø Toxemia is the circulation of bacterial endotoxins in the blood. It is observed in severe forms of diseases caused by Gr(-) bacteria that have endotoxin, for example, salmonellosis, escherichiosis, meningococcal and other infections. Often combined with bacteremia and sepsis.
The localization of the pathogen in the body also determines the routes of its elimination: with urine, feces, purulent discharge, sputum, saliva, mucus, blood, cerebrospinal fluid. Everything serves as diagnostic material. Knowledge of the source of infection, routes and methods of infection, and the properties of the pathogen form the basis of anti-epidemic measures.
The role of the macroorganism in the infectious process.
Susceptibility― a genetically determined trait, this is the ability to respond to the introduction of a microorganism by the development of an infectious process; associated with cell reactivity.
Resistance― resistance of the body, which is determined by nonspecific factors of anti-infective defense. Factors that weaken the body’s protective functions contribute to the spread of infection, and those that increase resistance prevent it.
Entry gates of infection- these are tissues that lack physiological protection against specific microorganisms (i.e., the place through which the microorganism penetrates the macroorganism).
Infection- one of the phases of development of the infectious process (terminal phase), its extreme degree of manifestation.
1. Etiology (each infectious disease is caused by a specific pathogen).
2. Contagiousness (contagiousness, infectiousness).
3. Epidemic (tendency to spread). Can be:
· sporadic diseases - isolated cases of disease in a given region;
· epidemics - outbreaks of disease of various sizes;
Pandemic - a disease spreads over large areas.
4. Specificity of localization in certain organs and tissues.
5. Specificity of transmission mechanisms .
Transmission mechanism― a method of moving a pathogen from an infected organism to a susceptible one.
Transmission factors― elements of the external environment that ensure the transfer of the pathogen from one organism to another (water, food, air, living arthropods, environmental objects).
Transmission routes― specific elements of the external environment or their combinations that ensure the entry of the pathogen from one organism to another under certain external conditions.
6. Repeatability or non-repeatability (as a result of the emergence of immunity.)
7. Cyclicity of the course (i.e. the presence of certain periods of the disease).
Periods of infectious disease
1) Incubation period― time from the moment of introduction of the pathogen into the body until the first clinical symptoms of the disease appear in the patient; The duration of incubation can vary greatly - from several hours, days, weeks, months - to several years.
2) Prodromal (period of warning signs of illness)) - characterized by the appearance of the first nonspecific symptoms (general weakness, headache, fever, chills, muscle pain, etc.)
3) The period of clinical manifestations (the height of the disease) - nonspecific as well as specific symptoms characteristic only of this disease are maximally expressed.
4) Exodus period:
· convalescence (full recovery with microbiological sanitation);
· convalescent microbial carriage;
· transition to a chronic form;
· death.
Forms of infections (infestations)
1. By the nature of the pathogen:- bacterial
Viral
Fungal
Protozoans
2. By the number of pathogens:- monoinfection
Mixed infection
3. According to the localization of the pathogen in the host body:
Local (focal)
General (generalized):
bacteremia (viremia)
· septicemia
· septicopyemia
toxic-septic shock
· toxemia
· toxinemia
4. According to the mechanism of occurrence (origin):
Exogenous
Endogenous
Autoinfection
5. Repeated diseases:
Reinfection
Superinfection
Secondary infection
Relapse
6. According to the main source of infection:
Anthroponoses (source of infection - humans)
Zoonoses (source of infection - animal)
Sapronoses (source of infection - external/abiotic environment)
7. According to the mechanism of transmission and localization of the pathogen in the body:
Intestinal with fecal-oral transmission mechanism
Respiratory tract infections with aerosol transmission
Blood pumps with a transmission mechanism
Infections of the external integument with a contact mechanism of transmission
8. By place of origin:- out-of-hospital
Intrahospital (HAI)
Natural focal
9. By distribution:
Sporadic cases
Epidemics
Pandemics
Endemics (attachment of an infectious disease to a specific region)
10. By duration:
Persistent (latent, chronic, slow)
10. According to the nature of the flow:
Asymptomatic (microbial carriage)
Erased (subclinical)
Manifest
Fulminant
Forms of infections - basic concepts.
Monoinfection- an infectious disease caused by one type of pathogen.
Mixed infection(mixed) - two or more types of pathogens cause an infectious disease.
Secondary infection- the initial (main) infection is joined by another infection caused by an opportunistic pathogen.
Reinfection― re-infection with the same pathogen after recovery against the background of unformed immunity.
Superinfection― re-infection with the same pathogen against the background of the current disease.
Relapse- recurrent disease due to endogenous infection.
At exogenous infection the pathogen enters the body from the environment (outside), when endogenous― is located in the body itself.
Autoinfection- endogenous infection caused by the body’s own opportunistic microflora.
Persistence― long-term presence of microorganisms in the body in an inactive state.
Microcarrier(bacterial carriage, virus carriage) - the presence (carriage) of a microorganism in a macroorganism without clinical manifestations of infection. It may be: healthy microbial carriage - develops in healthy individuals who have been in contact with patients or carriers of the corresponding pathogenic species; convalescent microbial carriage - a condition in which the release of the pathogen continues after the patient has clinically recovered; most often formed when post-infectious immunity is weakly strained.
Focal infection― an infection in which the process is localized in a specific organ or tissue and does not spread throughout the body. However, a focal infection with the slightest imbalance between macro- and microorganisms can develop into a generalized form.
Generalized infection― an infection in which pathogens spread predominantly through the lympho-hematogenous route throughout the entire macroorganism.
In this case, the following develops:
1) bacteremia - a condition of the body in which microorganisms circulate in the blood but do not multiply;
2) viremia - a condition of the body in which viruses circulate in its blood (generalized viral infection);
3) sepsis - the presence of microorganisms in the blood and their reproduction;
4) septicemia - a form of sepsis in which microorganisms circulate and multiply in the blood without the formation of secondary foci of infection;
5) septicopyemia - a form of sepsis in which microorganisms not only circulate and multiply in the blood, but also the formation of purulent metastatic foci in various organs;
6) toxemia - a condition of the body in which bacterial endotoxins circulate in the blood;
7) toxinemia - a condition of the body in which a bacterial exotoxin or other toxin circulates in the blood (with botulism, tetanus and other diseases);
8) with the massive entry of bacteria and their toxins into the blood, it develops bacterial or toxic-septic shock.
Epidemiology- the science of the epidemic process. Studies the emergence and spread of infectious diseases among the population.
Links of the epidemic chain:
1. Source and reservoir of infection.
2. Mechanisms and factors of transmission of pathogens (transmission factors can be water, food, air, etc.).
3. Susceptible organism.
By influencing these links, it is possible to prevent or even eliminate an epidemic process that has already arisen.
Table of contents of the topic "Infectious process. Classification of infections. Epidemiology of the infectious process. Epidemic process.":1. Bacterial carriage. The ability to survive long-term in the body. Infectious process. Infection. Infectious disease.
2. Conditions for the development of infection. Pathogenicity. Infectious dose. The rate of reproduction of microorganisms. Entrance gate of infection. Tropism. Pantropism.
3. Dynamics of the infectious process. Bacteremia. Fungemia. Viremia. Parasitemia. Sepsis. Septicemia. Septicopyemia. Toxinemia. Neuroprobasia.
4. Features of infectious diseases. Specificity of infection. Contagiousness. Infection contagiousness index. Cyclicality. Stages of infectious disease. Periods of infectious disease.
5. Classification (forms) of infectious diseases. Exogenous infections. Endogenous infections. Regional and generalized infections. Monoinfections. Mixed infections.
6. Superinfections. Reinfections. Recurrence of infection. Manifest infections. Typical infection. Atypical infection. Chronic infection. Slow infections. Persistent infections.
7. Asymptomatic infections. Abortion infection. Latent (hidden) infection. Inapparate infections. Dormant infections. Microcarrier.
9. Classification of infectious diseases according to Groboshevsky. Population susceptibility. Prevention of infections. Groups of activities for the prevention of infectious diseases.
10. Intensity of the epidemic process. Sporadic incidence. Epidemic. Pandemic. Endemic infections. Endemic.
11. Natural focal infections. Parasitologist E.N. Pavlovsky. Classification of natural focal infections. Quarantine (conventional) infections. Particularly dangerous infections.
Features of infectious diseases. Specificity of infection. Contagiousness. Infection contagiousness index. Cyclicality. Stages of infectious disease. Periods of infectious disease.
Infectious diseases are characterized specificity, contagiousness And cyclicality.
Specificity of infection
Every infectious disease caused by a specific pathogen. However known infections(for example, purulent-inflammatory processes) caused by various microbes. On the other hand, one pathogen (for example, streptococcus) can cause various lesions.
Contagiousness of an infectious disease. Infection contagiousness index.
Contagiousness (infectiousness) determines the ability of a pathogen to be transmitted from one person to another and the speed of its spread in a susceptible population. For quantitative assessment of contagiousness, it is proposed infectiousness index- the percentage of people who have recovered from the disease in a population over a certain period (for example, the incidence of influenza in a certain city for 1 year).
Cyclicity of infectious disease
Development of a specific infectious disease limited in time, accompanied by a cyclical process and a change in clinical periods.
Stages of infectious disease. Periods of infectious disease.
Incubation period[from lat. incubation, lie down, sleep somewhere]. Usually, between the penetration of an infectious agent into the body and the manifestation of clinical signs, there is a period of time specific for each disease - incubation period, characteristic only of exogenous infections. During this period, the pathogen multiplies, and both the pathogen and the toxins it produces accumulate to a certain threshold value, beyond which the body begins to respond with clinically pronounced reactions. The duration of the incubation period can vary from hours and days to several years.
Prodromal period[from Greek prodromos, running ahead, preceding]. As a rule, the initial clinical manifestations do not bear any pathognomonic [from the Greek. pathos, disease, + gnomon, indicator, sign] for a specific infection of signs. Weakness, headache, and feeling of exhaustion are common. This stage of an infectious disease is called the prodromal period, or “precursor stage.” Its duration does not exceed 24-48 hours.
Period of disease development. At this phase, individual traits of the disease or signs common to many infectious processes appear - fever, inflammatory changes, etc. In the clinically pronounced phase, the stages of increasing symptoms (stadium wcrementum), flourishing of the disease (stadium acme) and fading of manifestations (stadium decrementum) can be distinguished. .
Convalescence[from lat. re-, repetition of action, + convalescentia, recovery]. The period of recovery, or convalescence, as the final period of an infectious disease, can be fast (crisis) or slow (lysis), and can also be characterized by a transition to a chronic state. In favorable cases, clinical manifestations usually disappear faster than the normalization of morphological disorders of organs and tissues and the complete removal of the pathogen from the body. Recovery may be complete or accompanied by the development of complications (for example, from the central nervous system, musculoskeletal system or cardiovascular system). The period of final removal of the infectious agent can be delayed and for some infections (for example, typhoid fever) can last for weeks.
