The entrance lecture. Peculiarities of infectious diseases. Classification. The notion about infection, kinds of infectious process. Principles of diagnosis and treatment of infectious diseases.
http://www.who.int/topics/infectious_diseases/en/
Nowadays there are about 2500 well-known microorganisms that cause infectious diseases. About 300 nosological forms have been distinctly described (‘nosos‘ means ‘disease’ in Greek). According to the international classification the infectious diseases relate to 13 classes and 975 rubrics. They constitute up to 60-70% of the total morbidity. In polyclinics 4-6 patients out of 10 suffer from infectious diseases. The responsibility for the exposure of the infectious morbidity is taken by the physicians of the «tirst line» – therapeutists, surgeons, gynecologists and other specialists. Now it is distinctly ascertained that the infectious agents are the basic or leading ethiological factor of the different branches of the medical science.
Besides these many new earlier unknown discuses have appeared. Only during the last years such infections diseases as HIV, Legionnaires disease, cryptosporidiosis, SARS, hemorrhagic fevers, caused by Marburg or Ebola virus, hantavirus and others have appeared, they are responsible for the development of the ulcer disease of the stomach, pneumonia, meningoencephalitis, cutaneous diseases, lymphoadenopathy, heart and vessels diseases. Many researchers think that the world is standing on the verge of the T-cell leucosis epidemic, which is already widely spread in
The origin of the infectious diseases dates back from the ancient times. The old archives that contain the man’s first descriptions of his thoughts with the help of signs tell us that he already suffered from such diseases as leprosy, hydrophobia, malaria, trachoma, fungous, helmintic and some other diseases.
The common feature of the majority of the infectious diseases is the possibility of transmission from the affected organism to a healthy one, and the ability of massive (epidemic) spreading. During the study of the infectious diseases the terms «infection» and «infectious process» are usually used. They both originate from the Latin words – «infectio» – «pollution», «contamination» and «infecio» – «to pollute». At the modern level of the science development it is impossible to give an exhaustive definition of the terms «infection» and «infectious process» which would open all the sides of this conception. The term ‘infection’ means the penetration of a microorganism into another organism and their following interaction under various conditions connected both with the microbe itself and the qualities of the organism which receives it at the various stages of the development of the organic world.
According to all of these definitions it is obvious that the term «infection» cannot be identified with the «intectious process». The contents which we put into the term «infectious process» does not let us make a complete image of the infection as a general biological phenomenon. The concept «infection» is much wider as infection is common to all the beings. The infectious process includes the patterns common to the complicated organisms. The term «infectious process» is used to identify all the dynamics of the pathologic changes connected with the infection irrespective of the fact that they develop into a special qualitative condition called an infectious disease or not.
The penetration of a certaiumber of microorganisms into the macroorganism is needed for the infectious disease to develop. Besides, it has to be of a certain quality i.e. pathogenicity and virulence. However, the development of the pathological process depends on the general condition of the macroorganism and its immune status. In case of the weak immune status the pathologic process develops rapidly and the disease takes a severe course, in case of the comparatively strong immune status the disease takes a mild course or may not develop at all. Spreading of the disease and its severity depend on the environment – both on the geographical position (in the tropics – overheating, in cold countries – supercooling), and on the social sphere (a luxury villa and overcrowded facilities). All these processes can be expressed in the formula: the infectious disease is pro rata to the number and quality of the microbe (pathogenecity, virulence) and invasively to the immune status and the environment. Each of the mentioned factors is variable and they should be considered as dynamically developing with the changing of the cause and effect.
Different interrelations occur when organisms contact with one another, it happens iature all the time. To understand the infectious diseases we should mention the basic types of such interrelations.
1. The meeting and contact of the organisms do not have any consequences, any reaction. No symbiotic relations appear after it. In such cases we talk about species inherited immunity. For example, a human immunity to the horned livestock’s plague, to the hemorrhage septicemia of cats and others.
2. The meeting of the organisms results in the symbiotic commonwealth. (in Greek «symbiosis» means state of living together). There may be no reaction at all on the part of both partners, the condition called saprophytosis («saprobe» means microorganism that lives in the dead organic remains) appears. Some researchers consider symbiosis to be any form of living together between the representatives of different species. To this symbiosis they refer:
a) synoikia (Greek) – neutral living together during which one species uses the other one as a place to live without harming it;
b) mutualism – the symbiosis that is profitable for both organisms;
e) commensalism (Lat. «com» – with, «mensa» – table) also (French –
«commensa» – dependent) interrelation when one organism gets a benefit
from the other without harming it;
d) parasitism – a microorganism feeds with the saps or tissues of the master
harming it. Most of the infectious diseases belong to this kind of symbiosis.
If the infectious disease is caused by one species of microorganism it is called simple. If two or more microbe agents participate in the disease, then we talk about mixed-infection. Joining one infection to the other may affect the infectious process in different directions sometimes intensifying it, sometimes decreasing its activity and manifestations. So while studying the infectious pathology we should consider not only the pathogen itself but their associations. Salmonella infection especially bent to join other infectious diseases and start the secondary pathological process, this phenomena is called nosoparasitism (in Greek «nosos» – disease).
Gathering the epidemiological anamnesis is as difficult as gathering the disease anamnesis, and the skill of collecting it needs to be developed just as the skill of objective examining, the more so as gathering the correct anamnesis is considered to be more difficult to learn than the procedure of the objective examination. At the inept approach to the patient and frivolous attitude to gathering the epidemiological anamnesis, the doctor cannot get the necessary information. Sometimes it is difficult to gather the correct anamnesis because in case of the disease with a long incubative period the patient and his relatives can forget some data, which are of the diagnostical and epidemiological value.http://papers.ssrn.com/sol3/papers.cfm?abstract_id=1520157
The following points are the most important for the epidemiological anamnesis:
2. The patient’s occupation. Thus the workers of cattle-breeding farms can more often get sick with brucellosis, the agricultural workers – with leptospirosis, hemorrhagic fever, tick epidemic typhus, the workers of rice fields are subject to the infection of ankylostomidosis and strongyloidosis.
3. The previous diseases and preventive vaccinations. This information is necessary as the previous diseases in a number of cases speak against the disease which is suspected at a given moment. However, it is always necessary to take into consideration that there is not a single infectious disease, which would not repeat, though in rare cases. Such diseases as flu, malaria, shigellosis, diphtheria, erypsipelas are the most recurring. And vice versa measles, epidemic typhus result in a firm and continuous immunity which guarantees from the recurrence of the diseases. The indications available in the anamnesis on the vaccination do not eliminate a possibility of the disease caused by the same infection, but in case of vaccination there are often distorted, atypical forms of the disease, the so called deleted forms. Having collected the data of an epidemiological anamnesis one starts to inquire about the main complaints and symptoms, paying attention to every detail in the sequence of their development.
http://health.mo.gov/training/epi/DiseaseProcess.html
The temperature rise can be fast (acute), when the patient clearly marks even the hour of the onset of the disease (ornithosis, leptospirosis, etc.). In case of the fast temperature rise, as a rule, the patient marks the chills of different express eness — from slight chills up to strong chills (in malaria, etc.). In other diseases the temperature rises gradually (typhoid, paratyphoids).
By the expressiveness of the fever there are distinguished the following conditions: a subfebrile condition (37,0 –
The nature of the temperature curve. The observation the dynamics of the fever increases its differential – diagnostic value. In some infectious diseases the temperature curve is so characteristic that it determines the diagnosis (malaria, typhinia). It is accepted to mark out several types of a temperature curve, which are of a diagnostic value.
The constant fever (febris continua) is characterized by the permanently high body temperature often up to
The remittent fever (f. remittens) is distinguished by daily fluctuations of the body temperature from more than
The intermittent fever (f. intermittens) is manifested by the correct change of the high or very high and normal temperature with daily fluctuations of 3 —
The relapsing fever (f. recurrens) is characterized by the correct change of the high-fever and fever-free periods that last several days (typhinia, etc.).
The undulating or undulant, fever (f. undulans) is distinguished by a gradual increase of the temperature up to the high points and then its gradual decrease to the subfebrile and sometimes normal temperature; in 2 — 3 weeks the cycle is repeated (visceral leishmaniasis, brucellosis, lymphogranulomatosis).
The hectic (exhausting) fever (f. hectica) — a prolonged fever with considerable daily fluctuations (3 —
The irregular (atypical) fever (f. irregularis) is characterized by large daily amplitude, a various degree of a temperature increase, an indeterminate duration. It stands closer to the hectic fever, but does not have a correct nature (sepsis, etc.).
The distorted (inverted) fever (f. inversa) is distinguished by a higher morning temperature than the evening one.
Besides these generally accepted types we consider expedient to name two more: an acute undulating fever and a relapsing one.
The acute undulating fever (f. undulans acuta) in contrast to the undulate one is characterized by relatively short waves (3 — 5 days) and by the absence of remissions between the waves; the usual temperature curve represents a series of damped waves, i.e. each subsequent wave is less expressed (in the altitude and duration) than the previous one (typhoid, ornithosis, mononucleosis, etc.): when the subsequent wave is caused by adding of a complication, the revertive interrelations are observed, i.e. the second wave is more expressed, than the first one (epidemic paratitis, flu, etc.).
The relapsing fever (f. recidiva) in contrast to the recurrent fever (the correct alternating of the fever waves and apyrexy) is characterized by a relapse (usually one) of the fever which develops in different terms (from 2 days to one month and more) after the termination of the first temperature wave (typhoid, ornithosis, canicola fever, etc.). The relapses develop in some of the patients (10 — 20 %). In this connection if the relapse has an important diagnostic value, the absence of it does not eliminate a possibility of the mentioned above diseases at all.
Each infectious disease can have different variants of a temperature curve, among which some are more frequent, they are typical for this or that nosological form. Sometimes they even allow to diagnose the disease quite accurately (tetrian fever, etc.).
For the differential diagnostics the interval between the onset of a fever and the appearance of organic lesions is particularly important. In some infectious diseases this period is less than 24 hours (herpetic infection, scarlatina, rubella, meningococcemia, etc.), in others it lasts from 1 up to 3 days (measles, shigellosis etc.), and, at last, in a number of diseases it lasts more than 3 days (typhoid fever, virus hepatitis, etc.).
The nature and level of the infectious sickness rate also matters. For example, any feverishness during the epidemic of flu suggests a possibility of flu. The indication to the contact with the people sick with measles, scarlatina, water-pox, rubella and other droplet infections is important. These data are compared to the terms of an incubation period. Other epidemiological data (the stay on the territory which is endemic on malaria, and other diseases) also matters.
For the differential diagnostics the change of a temperature curve under the influence of etiotropic medications is important. Delagilum stops malarial attacks, in endemic typhus the temperature quickly becomes normal after the reception of tetracyclines and others. There are a number of peculiarities of the fever syndrome, which one can use for the differential diagnostics. The differential diagnosis of a fever needs to be done to distinguish it from the body temperature rising of another nature (thermal shock, hyperthyroidism).
The second component which is not less important for the diagnostics and differential diagnostics of the infectious diseases is a rash on the skin – exanthema. It is because the rashes are a symptom of many infectious diseases, besides, they are well visible, quite often catch one’s eye even at the first examination of the patient.
There are exanthemas, characteristic of this or that infectious disease and they are an obligatory component of a clinical symptomatology of this or that infectious disease.
The expressiveness and nature of exanthemas can be miscellaneous and are not always observed in other infectious diseases. In this connection their presence or absence in different infectious diseases essentially differs.
The exanthemas in infectious diseases are rather diverse. They differ iature of different elements of an eruption, localization, terms of appearance, stages of a rash, the dynamics of development of separate elements, etc. All these features are taken into consideration while making a differential diagnosis. In the diagnostics process the legible definition of separate elements of an eruption and unified comprehension of the terms are very important. The dermatologists and the infectionists do not always define some elements of an eruption in the same way. The following nomenclature is generally accepted in infectious diseases.
Roseola — a small spot (diameter 2 —
The so-called punctate rash is close to roseola. It consists of a set of shallow (in a diameter of about
The macule (macula) represents an element of the eruption similar to the roseola, but larger (5 —
Papule (papula) — a superficial formation without a cavity, rising above the level of the skin. It has a mild or dense consistence, the reverse development ends without the formation of a scar. There are inflammatory and noninflammatory papules. In the infectious diseases only inflammatory ones occur. They are caused by the proliferation of epidermis and infiltrate development in the papillary layer of derma with vasodilatation and limited edema. Papulas have the same color as roseola and macula. There are papulas of a different size (1-
Erythema — is vast fields of the bloodshot skin which are red, purple-red or magenta. The erythema is formed as a result of large maculae joining. Therefore the erythema has festoon blurry edges. inside arithmetic fields there can he separate fields of the skin with normal coloring. There is no expressed inflammatory process.
Unlike the infectionists the dermatologists consider that the term “erythema” means inflammatory fields with a diameter from
Tubercle (tuberculum) — a formation without cavities which arise as a result of the development of an inflammatory infiltrate of granulematous constitution in derma. The hillock differs from a papule, it lies deep in the derma and the infiltrate is determined at the palpation. The hillocks have legible borders and a tendency to grouping. As against papules at further development the hillock can narcotize, forming ulcers and leaving a scar. The hillocks develop in dermal and visceral leishmaniasis, deep mycosis.
Node (nodus) — a limited dense formation with a diameter from 1 up to
In some cases they disappear without any traces (nodal erythema), in chronic illnesses they ulcerate and heal leaving a scar.
Wheal (urtica) – an element of an acute inflammatory nature that has no cavity. There develops an acute restricted edema of the skin papillary laver. It develops owing to the trichangiectasia of the papillary layer of derma, the increase of their penetrability and the outcome of protein-free exudation through a vascular wall, which then compresses the vessels. As a result dense formations of different size and form suddenly develop on the surface of the skin and rise above its level. The cyanolic porcelain-white coloring in the center and the pink-red one on the peripherals are typical. An itch and a burning sensation of the skin appear with the development of a blister. The blisters develop in a serum disease, medicinal allergy and sometimes in some infectious diseases (leptospirosis, virus hepatitis, etc.
Vesicle (vesicula) — a small cavity formation containing serouse, less often serouse-hemorrhagic fluid. The blister develops directly in the false skin, under the corneous layer, in middle or on border with derma. It rises above the level of the skin as a half-round element with a diameter from 1,5 up to
Herpetic eruption (herpes) — a bunch of small closely set bubbles on the erythematic inflammatory base (herpetic infection, surrounding deprive, etc).
Pustule (pustula) is also a blister but its contents is cloudy (purulent) because of a clump ofa big amount of leucocytes.
Blister (bulla) — a cavity formation with a dimension of more than
The vesicles can be situated on the background of the inflamed skin (a violent form of erysipelas, anthrax, multiform exudative erythema, Stivens — Johnson syndrome, etc.).
Hemorrhages (hemorrhage) — an extravasation into the skin of different kinds and dimensions. They develop as a result of the erythrocytes yield from veins to the ambient connecting tissue of derma or hypodermic fatty tissue. It can be a result of the damage (breakage) of the vessel or heightened permeability and fragility of a vascular wall.
According to the value and form hemorrhages are divided into the following elements: petechias (petechiae) — dotted hemorrhages on the background of the normal skin (primary petechias) or on the background of roseolas (secondary petechias); purpura (purpura), in which the dimensions of the elements oscillate from 2 up to
Ecchymoses (sugillationes) — hemorrhages on places of injections that are not the sort of an exanthema but have a diagnostic value as a parameter of a heightened fragility of vessels, that is often observed in the development of a hemorrhagic syndrome.
The hemorrhagic elements of the eruption are observed in many infectious diseases and have a great value both for the differential diagnostics and for the evaluation of the illness severity.
All the reviewed above exanthemas belong to the primary morphological elements of the eruption. However, the secondary morphological elements of the eruption also have a diagnostic value. The dyschromias of the skin, flake, peel, anabrosis. ulcers, seams belong to them.
Erosion (erosio) —a defect of the epidermis which develops after opening of the cavity primary elements (vesicles, pustules, vesica). The bottom of the erosion is covered with epidermis or partially with the papillar layer of the derma. By the size and form the erosion corresponds to the primary element. After healing the erosion do not leave any stable changes of the skin.
Ulcer (ulcus) —a deep defect of the skin which affects the epidermis. derma, and sometimes underlying tissues. The ulcers develop as a result of the disintegration of the primary infiltrating elements in the deep parts of the derma — pimples, clusters, and the opening of the deep pustules. The form and the edges of the ulcer are of great importance for the differential diagnostics. The edges of the ulcer can be undermined, vertical saucer-shaped, callous, mild, etc. The ulcer always heals leaving a cicatrix. The ulcers develop both in the infectious diseases (dermal leishmania.sis, anthrax, tularemia, etc), and in the illnesses related with the competence of other specialists (lues, tuberculosis, trophic ulcers, neoplasm).
Skin dischromia (dyschromia cutis) — a disorder of the pigmentation, which develops on the place of the resolved morphological elements of the dermal eruption. The expressiveness and duration of the hyperpegmentation are various. As a rule, pigmentary spots are brown. Sometimes they are sharply distinguished, for example, after measles maculepapulas eruption, especially in case of its hemorrhagic impregnation. Sometimes it is only a hardly noticeable brown blot (for example, on the place of typoid roseola), which disappears fast and does not leave any traces.
Scale (squama) is a loosened tearing away ceel of the corneous layer, which lost its connection with the underlying epidermis. Depending on the size of the flakes there is micro- and macrolaminar pityriasis.
Small-laminar, branny pityriasis (desquamatio pityriasiformis) is observed in measles, branny lichen. The smallest flakes get detached and the skin looks as though it is powered with flour.
Macrolaminar pityriasis (desquamatio lamallosa) is characterized with a larger dimension of the flakes, and they can get detached from the skin by the whole layers. The similar pityriasis is characteristic of scarlatina. pseudotuberculosis, toxidermias, etc. The pityriasis develops in the period of convalescence from the infectious diseases and what is important for differential diagnostic – in the late period of illnesses or during reconvalescence.
Crust (crusta) a product of thickening and desiccation of different kinds of other elements exudates of the eruption (pustules, vesicles, anabroses, ulcers). There are serouse crusts (semidiaphanous or grayish), purulent (yellow or green-yellow) and hemorrhagic (brown or dark red). The size of the crusts corresponds to the size of the preceding element.
Cicatrix (cicatrix) – coarse-fibroid growth of the connecting tissue, w hich substitutes deep defects of the skin.
The listed above elements of exanthema are basic and can be observed in infectious diseases, the differential diagnostics is based on their exposure. In case of the eruption it is necessary to identify the type of separate elements and, besides, to specify other peculiarities of exanthema.
The very important signs are the terms of the eruption development.
The localization of the eruption elements and the place of the greatest concentration of exanthema are of a diagnostic value. In some cases the sequence of the rush development is of the diagnostic value. The duration of the eruption elements existence is also important. Repeated rashes and the inclination for joining the elements of the eruption can be of a diagnostics value.
Enanthema – the rashes on the mucous – can he observed less often in infectious diseases and is less important for the differential – diagnostic value. However, in a number of illnesses the changes of the mucous are rather informative at their identification at the initial stage. The lesions of the oral cavity and eyes mucous are of the greatest practical value.
The most essential symptoms characteristic of the infectious diseases are the hyperadenosises, icterus, catarrh of respiratory paths, diarrhea. meningeal symptoms.
The improvement of the infectious diseases diagnostics is closely connected with the development of microbiologic, gene-diagnostic. immunological methods of investigation. The latest methodological achievements allow not only to essentially raise the level of etiological confirmation of the diagnosis, but also to present the detailed characteristic of the microbe behavior in the organism. In particular, it is not possible to judge about the quantity of microbial bodies in different substrates of the organism, to determine the availability and concentration of antigens, toxins and even separate molecules of the microorganism. The gene-diagnostics opens especially wide possibilities, however, the biosensory (including immunosensory) methods of investigation, which are already being worked out in a number of the countries, are next in turn.
But a great number of the laboratory investigations that are available for a doctor are not always important for the diagnosis and are sometimes overestimated and distracts the attention from the clinical diagnostics that is also very important. The clinical examination of the patient is of primary importance and the laboratory and instrumental methods are supplementary. Every laboratory test should be evaluated according to its specific features, sensibility and informativity, it is necessary to determine the indications and terms of the investigations in different nosologic forms and to state their comparative diagnostic value.
The treatment of infectious diseases is a more complicated task in comparison with therapy of other palhologic conditions as besides the correction of the disorders in the function of the organs and systems, it has a complicated task – to eliminate and suppress the infectious agent.
In the historical aspect only from the 17th century when the improvement of the agricultural production resulted in a better nutrition, it had an immediate effect on the outcome of some infectious diseases. At the beginning of the 19lh century the improvement of the sanitary-hygienic control over food and water resulted in the decrease of many infectious diseases transmission. Later the knowledge of the specific etiology of the infectious diseases promoted the creation of the scientific base for their prevention and treatment. In the 20th century when the methods of immunization were widely used and especially when the antibiotics appeared the morbidity and mortality from infectious diseases were considerably reduced. The children’s mortality was sharply reduced. The lifetime in the developed countries increased from 47 years on the average till 70 years.
Despite the increasing role of the microbial factor under different pathologic conditions, the practice of treating patients in polyclinics and somatic hospitals has not changed essentially. The treatment of the patients is mainly based on trial-and-error assigning the coolest or the most available antibiotic, as there are no real possibilities and the doctors striving to study the development of the infectious process in dynamics. At its best a single-pass serological or microbiologic research revealing the infectious agent is used as a sufficient argument for the statement of the clinical diagnosis and assigning the therapy. Therefore it is not surprising that there is no noticeable progress in outcomes of treatment, and there is an increase of negative consequences such as the medical disease, immunodefence disorders, development of dysbacteriosis, appearance of polyrefractory microorganisms.
Due to the technological achievements a large number of antibacterial and antiviral drugs have been made. The availability of drugs considerably dilates therapeutic capabilities, but also demands a scientifically reasonable differentiated approach.
The semi-centennial experience of the antibiotic therapy in the infectious disease treatment has not justified the initial hopes. After a considerable increase of the treatment efficiency of bacterial infections in the 50-60s, despite the appearance of a broad spectrum of new antibiotics. the multiple increase of uptaken doses, there have beeo adequate progress in the results of treatment, but the number of cases of the drugs intolerance and therapy complications have increased.
The indispensable condition of the therapy efficiency is the differentiated approach to drugs in dependence on the way they act, capability to the intracellular infiltration, bacteriostatic or bactericidal influence.
http://www.scribd.com/doc/13573922/5/Classification-of-Infectious-Diseases
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http://www.scribd.com/doc/13573922/5/Classification-of-Infectious-Diseases
