№ 33 ARVI pathogens. Taxonomy. Characteristic. Laboratory diagnostics. Specific prevention and treatment.
Taxonomy and classification:
RNA viruses. Family I - Paramyxoviridae includes human parainfluenza viruses (5 serotypes) and respiratory syncytial virus (PC);
Family II - Picomaviridae includes 7 serotypes of Coxsackie and ECHO enteroviruses affecting the respiratory tract, and 120 serotypes of rhinoviruses;
III family - Reoviridae includes 3 serotypes that cause diseases of the respiratory and gastrointestinal tracts;
IV family - Coronaviridae includes 3 serotypes that also affect the respiratory and gastrointestinal tracts.
DNA containing viruses. Family V - Adenoviridae. Representatives of this family affect the eyes, intestines, bladder, 3 types of adenoviruses cause SARS.
Structure: . Medium size, spherical, rod-shaped or filiform. Most ARVI pathogens contain single-stranded RNA, except for reoviruses with double-stranded RNA and DNA-containing adenoviruses. Some of them are surrounded by a supercapsid.
Antigenic structure
: complex. Viruses of each genus have common antigens; viruses also have type-specific antigens, which can be used to identify pathogens with a serotype. Each group of ARVI viruses includes a different number of serotypes and serovariants. Most ARVI viruses have a hemagglutinating ability. RTGA is based on blocking the activity of hemagglutinins of the virus with specific antibodies.
cultivation
: The optimal model for cultivation is cell culture. For each group of viruses, the most sensitive cells were selected (for adenoviruses, embryonic kidney cells; for coronaviruses, embryonic and tracheal cells). In infected cells, viruses cause CPE (cytopathic effect). Cell cultures are also used in the identification of pathogens with cytolytic activity (for example, adenoviruses). For this, the so-called biological neutralization reaction of viruses in cell culture (RBN or PH of viruses) is used. It is based on the neutralization of the cytolytic action of viruses by type-specific antibodies.
Immunity: neutralizing specific IgA (provide local immunity) and cellular immunity. Local production of a-interferon, the appearance of which in the nasal discharge leads to a significant decrease in the number of viruses. An important feature of SARS is the formation of secondary immunodeficiency. Post-infectious immunity is unstable, short-lived, type-specific. A large number of serotypes and a variety of viruses - a high frequency of recurrent infections.
Microbiological diagnostics.
The material for research is nasopharyngeal mucus, imprint smears and swabs from the pharynx and nose.
Express diagnostics. Detect viral antigens in infected cells. RIF is used (direct and indirect methods) using specific antibodies labeled with fluorochromes, as well as ELISA. For difficult-to-cultivate viruses, a genetic method (PCR) is used.
Virological method. Indication of viruses in infected laboratory models is carried out by CPE, as well as RHA and hemadsorption (for viruses with hemagglutinating activity), by the formation of inclusions (intranuclear inclusions in adenovirus infection, cytoplasmic inclusions in the perinuclear zone in reovirus infection, etc.), as well as by the formation of "plaques", and "color test". Viruses are identified by antigenic structure in RSK, RPHA, ELISA, RTGA, RBN viruses.
Serological method. Antiviral antibodies are examined in paired patient sera obtained at intervals of 10 days. The diagnosis is made by increasing the antibody titer by at least 4 times. At the same time, the level of IgG is determined in such reactions as RBN of viruses, RSK, RPHA, RTGA.
Treatment: effective etiotropic - no; nonspecific - a-interferon, oxolin (eye drops), with a secondary bacterial infection - antibiotics. The main treatment is symptomatic / pathogenetic. Antihistamines.
Prevention: nonspecific - anti-epidemic. Events. Specific - no. For the prevention of adenoviruses - oral live trivalent vaccines.
History of virology.
The founder of the doctrine is Ivanovsky. He worked at the Nikitsky Botanical Garden and discovered there that the viruses that infect plants are not bacteria. The pathogen passes well through the filters. 6 years after the discovery, his data were confirmed.
Lefleur established the viral etiology of many diseases (for example, foot and mouth disease).
SARS.
ARVI includes many diseases with damage to the respiratory system and an aerogenic transmission mechanism. ARVI includes about 200 viruses: influenza, parainfluenza, RS-B (respiratory syncytial virus), rhino-, corona-, reo- and adenoviruses. According to the classification, they belong to different families. When diagnosing, there are methods for each virus.
The influenza virus can infect the upper and lower respiratory tract. The outcome of the disease can be even fatal.
ARI affects ≈ 18.6% (i.e. 18,609: 100,000 of the population), influenza ≈ 4% (i.e., 4,000: 100,000 of the population).
Flu.
Gripper (French) - to grasp, grab.
This is an acute highly contagious mass viral infection with an aerogenic mechanism of transmission. It is characterized by a combination of inflammatory changes in the upper respiratory tract and more severe and prolonged symptoms of general intoxication (periodically takes on an endemic and pandemic character).
Epidemiology.
Influenza epidemics were observed in the XII and XIV centuries. in Europe.
According to statistics, influenza epidemics occur every 2-3 years, pandemics every 10-12 years. From 1889 to 1890, the first pandemic was registered in Russia. She originated from China. A year and a half later, it spread to all continents. It was caused by the type A influenza virus.
In 1812, a flu pandemic called "Spanish Flu" was recorded. Its origin is also from China. It was caused by the same virus. More than 500 million people have been ill, more than 20 million have died.
The third pandemic was observed in 1947-1949. Called by the same type.
In 1957 - "Asian flu". More than 2 billion people have been ill, more than 1 million have died.
5th pandemic in 1968. Caused by the Hong Kong virus type A.
6th pandemic in 1977. Only young people got sick, because. the causative agent belonged to subtype A 1 and those who had been ill during the 5th pandemic had strong immunity.
The causative agent was isolated in 1931 (after the 2nd pandemic) by Shop (an English scientist) from sick pigs. The causative agent was named - influentio.
In 1933, Andrews and Villierne Smidt confirmed Chope's work. They were working on ferrets, infecting them with the flush that Shope worked with.
taxonomic position.
Family: Ortomixoviridae
Types: A, B, C (divided by RNA).
Type A - has many antigenic variants, tk. surface antigens are highly variable.
Type C - differs in a number of properties and stands out in a separate genus.
Genus: type C - influenza C
Type A and B - influenza virus A et B
In 1980, the WHO committee adopted a new classification of type A virus according to the content:
N-hemagglutinin (1-2);
Na-neuromenidases (1-9);
Subtypes are known: A 1 (H 1, Na 1), A 2 (H 2, Na 2), A 3 (H 3, Na 2).
To identify the pathogen, its description is required:
1) type of virus;
2) natural host;
3) the geographical origin of the strain;
4) its serial number;
5) its year of isolation and antigenic features.
For example: A (duck / USSR / 695/76 / H 3 / Na 2).
The structure of the virus.
The shape of the virion is close to spherical. Diameter 80 - 120 nm. The type of symmetry is spiral. They have an outer shell, which consists of 3 layers (inner - nucleoprotein, middle - membrane protein and lipid bilayer, inner - low molecular weight protein M 1). Spikes protrude from the outer membrane (there are up to 900 of them on the surface of one virion).
Н>Na by 4–5 times.
Genome.
The genome of viruses A and B is segmented single-stranded DNA, which consists of 8 segments. Each segment is an individual gene that is responsible for 1 or more properties. The genome codes for up to 10 proteins.
The C virus genome consists of 7 fragments. Chemical composition:
Viruses cannot reproduce themselves without a host cell.
Antigenic structure.
3) Ribonucleoprotein
main specific antigen. Contained in the outer shell. Responsible for adsorption on host cells (therefore it is more than Na). On the cell surface, it binds to mucoprotein receptors (which are also found on red blood cells). This is an antigen that is subtyped (the type is determined by RNA). It is the main target for the production of specific antibodies (which neutralize the virus). RA is used to identify the virus.
It is an antigen and an enzyme at the same time. The enzyme breaks down neuroamino acid (ensures the passage of the virus into the cell, as it breaks down the cell wall). Ensures the release of young virions from the cell. The virulence of the virus is associated with Na. Type C-Na is absent. Antibodies to Na partially neutralize the virus.
Processes of genetic change of a virus.
1) SHIFT processes (radical changes at the gene level);
2) DRIFT processes (point changes within a gene).
Every 2-3 years changes are caused by drift and every 10-12 years by shift (cause pandemics).
Ribonucleoprotein.
The main internal protein that forms the subunits of the capsid. Its functions: regulatory during transcription and genome replication. It is type specific. Antibodies have no protective effect against it.
resistance.
Unstable in the external environment, tk. all physical factors kill him. However, it is stored for a long time at temperatures from 0 to 4 ° C. Sensitive to alcohol and ether.
Reproduction.
The virus enters the host cells, the process of adsorption begins. After the virus is connected to the cell, Na enters the process, → the virus enters the cell, the supercapsid membrane opens, the virus is injected into the cell. There it penetrates to the core. On the nuclear envelope, the virus “undresses” (removes the capsid membrane) and the RNA of the virus penetrates into the nucleus, → to the integration of the virus into DNA, → to the self-production of individual structures of itself. Then they themselves gather and begin to be absorbed into the virus.
Virions can exit the cell by "explosion" or by budding. One offspring occurs after 6 - 8 hours. 1 virus produces 10 3 virions (therefore short incubation period).
Cultivation.
1) developing 10 - 11-day chicken embryo;
2) primary culture of human embryonic kidney cells;
3) in the culture of transplanted cells (Helo and KV);
4) in the body of animals (mice, hamsters, ferrets).
When grown in cell culture, indication can be determined (by color sample and cytopathic action (CPE) of the virus on the cell).
According to the RSC, we determine the type.
According to RTGA - we determine the subtype.
In the course of our discipline, we do not consider in detail the issues of treatment. This is the task of clinical departments, but you should be aware of the most general principles of infectious disease treatment. Treatment of all diseases, including infectious ones, can be of three types: symptomatic, pathogenetic and etiotropic.
Simp tomato treat The treatment is based on the use of medicinal preparations in accordance with the system of the disease - for pain - give analgesics, at elevated temperature - antipyretic, etc. Usually, when applying symptomatic treatment, we try to alleviate the patient's condition, often without taking into account the etiology and mechanism of development of the pathological syndrome. Strictly speaking, if symptomatic treatment has an effect, it becomes pathogenetic.
Patoge netic therapy I am aimed at the normalization of disturbed physiological functions of the body. This is one of the essential ways to treat infectious diseases. In some cases, in the absence of etiotropic therapy, correctly performed pathogenetic treatment is the main one, for example, in the treatment of most viral diseases. Pathogenetic therapy also plays a significant role in bacterial infections.
For example m er, in cholera, the leading link in pathogenesis is tissue dehydration due to the action of cholera exotoxin, cholerogen. Only properly performed rehydration therapy ensures the success of the treatment, and we are not talking about the simple introduction of liquid with a drink or parenterally. At the Department of Infectious Diseases, you should get acquainted in detail with this method of treatment, this is all the more important because the staff of the department has experience during the last cholera pandemic.
Etiotr opnaya therapist Iya is directed to the cause of the disease, the etiological factor, the pathogen and the products of its vital activity and decay. specific ical etiotropic therapy - to lay downeni With serum preparations, immune sera and immunoglobulins, antibodies from them act specifically on the pathogen and its toxins. With some reservations, vaccine therapy should be attributed to specific etiotropic therapy. However, in the case of vaccine therapy for chronic diseases of microbial etiology, the therapeutic effect is usually achieved due to both specific stimulation of the immune system and a significant non-specific stimulating effect. Phage therapy is also a specific etiotropic therapy, but it is currently used relatively rarely.
Nespets Physical etiotropic therapy - cheni e antimicrobial drugs (antibiotics, sulfonamides, chemotherapy drugs). Please note that antibiotic treatment is not a method of specific therapy, since there is not a single antibiotic that would affect only one type of pathogen.
When independently studying individual topics, it is necessary to pay attention mainly to specific etiotropic therapy, since antibiotic therapy is used in almost all bacterial infections.
5. Principles of prevention of infectious diseases The main direction of modern medicine is preventive. Prevention of infectious diseases is carried out by carrying out activities aimed at breaking the epidemic Main circuit: source IR infection - mechanism of transmission - susceptible population. Prevention can be specific and non-specific.
specific preventive measures Xia when using specific preparations: vaccines, serums, phages. The most important is active immunization with vaccines. At the last lecture on the course of immunology, we discussed the issues of vaccination, we only remind you that vaccine prophylaxis happens planned and according to epidemiological indications. We always pay attention first of all to your knowledge of vaccines used for routine prophylaxis. It will be useful once and for a long time to learn the routine vaccination calendar adopted in Ukraine, it will be useful not only for studying our subject, but also in the future. Seroprfi lactic acid mainly om is used for emergency prevention of the disease in individuals for whom the risk of infection is high. In the study of each topic, it is necessary to pay attention to the use of vaccines and sera for the prevention of diseases, since this constitutes an important section of our discipline.
We emphasize that specific prevention is aimed at breaking the epidemic chain in the last link, it should make the population immune to the corresponding infectious disease.
Nonspecific ical prophylaxis There is a set of measures that is the same for the prevention of all infectious diseases with the same route of transmission. It is aimed at all three links of the epidemic chain.
Impact on the first link - source and infections, concluding tsya in the early detection, isolation and treatment of patients and carriers. Identification of patients is not only the diagnosis of diseases in patients who seek medical help, but also a directed systematic examination of decreed contingents for intestinal infections, venereal diseases, hepatitis, AIDS, etc. Isolation of identified patients is carried out in infectious diseases hospitals and at home, in student dormitories - in insulators, etc. Separation can also be attributed to isolation - the closure of children's institutions for quarantine, a ban on visiting hospitals, the cancellation of mass events during an epidemic (for example, influenza), etc. The whole range of measures, including those for especially dangerous infections, will be discussed in more detail at the Department of Epidemiology .
Impact on the second link of the chain - mechanisms and transmission factors, conducts Xia depending on the route of transmission in different ways. To interrupt fecal-o ral path In order to prevent infection, it is important to ensure sanitary control of water supply and sewerage in settlements, public catering networks, monitor compliance with sanitary and hygienic standards in trade, food production, fight the spread of flies (timely yard garbage collection, use of closed containers for collecting garbage), etc. It is important to carry out current and final disinfection. Interrupt air-to apelle path dachas are possible due to the separation of the population, wearing gauze masks, airing and treating indoor air with ultraviolet rays (quartzization), etc. The transmission path the dacha is interrupted by the destruction of blood-sucking insects and the treatment of their breeding grounds (for example, with malaria, as it was dealt with in the course of biology), the use of repellents, window screening, etc. Contact way before Achi is interrupted due to personal hygiene and sanitation in everyday life, the use of condoms to prevent the transmission of sexually transmitted diseases, etc. Transmission of infection t placentally interrupted due to the control of pregnant women for a number of diseases (syphilis, AIDS) transmitted from mother to fetus. We now name only some methods of nonspecific prophylaxis, this material will be radiated in full by students at the Department of Epidemiology.
The third link in the epidemic chain is susceptible population. His protection from infection in the first place should be in sanitary and educational work. People should be informed about the unfavorable epidemiological situation through television, radio, newspapers, health bulletins in clinics, leaflets, posters, etc. In some cases, emergency non-specific drug prophylaxis (with antibiotics, antimalarial drugs) is carried out, which is essentially a preventive therapy after a possible infection.
It should be understood that none of the preventive measures taken ensures 100% success, therefore, prevention must be comprehensive, using all the possibilities of specific and non-specific prevention.6. DIAGNOSTICS OF INFECTIOUS DISEASES
The microbiological service in the system of practical health care mainly performs the task of microbiological diagnosis of infectious diseases and non-infectious diseases of microbial etiology. In practical classes, students study the methods of microbiological diagnosis of specific diseases, taking into account the characteristics of the biological properties of the pathogen and the course of diseases. At the lecture, we will consider the general principles of microbiological diagnostics and its place in the diagnostic activity of a doctor.
Diagnosis of an infectious disease, like any other, begins with anamnesis. Next comes the objective (examination, palpation, percussion, auscultation) and instrumental examination (temperature measurement, ECG, endoscopic, X-ray, ultrasound, etc.), clinical and laboratory (blood, urine, feces, biochemical, cytological examinations, etc.) . In addition to these methods, when establishing the diagnosis of an infectious disease, it is also necessary to take into account the epidemiological situation at this time and in this area. In areas endemic for certain infections, the direction of the diagnostic search will be appropriate. During an epidemic of an infectious disease, of course, differential diagnostics will be carried out first of all, taking into account vigilance for influenza, typhoid fever, cholera, etc. It is clear that we began to think about AIDS as a possible diagnosis only now that we know the epidemiological situation in the world and in our country.
Usually, the use of these diagnostic methods should lead to the establishment of a preliminary diagnosis and the appointment of treatment and an appropriate anti-epidemic regimen. Microbiological examination at this stage does not always help diagnosis, since it requires a long time, and express methods play only an auxiliary role. Therefore, most often treatment begins before an accurate diagnosis is established and without using the results of microbiological studies.
I want to emphasize that the diagnosis of the disease is established not by the laboratory, but by the clinician. I do not want to belittle the importance of my specialty, but it is important to understand that the responsibility for the correct management of the patient lies with you, the future practitioners. And in order to make an accurate timely diagnosis and prescribe adequate therapy, you need to skillfully use the results of microbiological studies, know their capabilities and limitations, choose the right time to prescribe a certain study and the test material, be able to collect it and send it to the microbiological laboratory.
We must outline the basic principles of microbiological diagnostics, which you must clearly understand. In the future, when studying individual infections, you will use these general principles for a better understanding and memorization of the material, paying attention to the main differences in diagnosing a particular disease from classical microbiological diagnostic schemes. This method of studying educational material is the most effective.
First of all, we note that the only The basis for the microbiological diagnosis of any infectious disease is the direct or indirect detection of the pathogen in the body. For clarity, we show you a table of the main methods of microbiological diagnosis of bacterial infections (Table 1).
Direct determination of the pathogen in the body and its identification (species determination) is possible using microscopic, bacteriological and biological diagnostic methods. It is necessary to distinguish between the terms "diagnosis" and "research". If the term “microscopic diagnosis” is used, this means that the microbiological diagnosis is established on the basis of a microscopic examination of the material from the patient, the pathogen was found in this material as a result of microscopy and its identification was carried out by morphological and tinctorial properties. Accordingly, the reliability of the diagnosis can also be assessed.
Microscopic examination can be not only an independent method of establishing a diagnosis, but also a stage of other research and diagnostic methods. For example, in bacteriological diagnostics, microscopic examination of smears from the test material, a colony, an isolated pure culture is repeatedly carried out, but the basis for the diagnosis is the isolation of the culture and its identification by a set of properties. Similarly, serological examination can be a step in the identification of isolated pure cultures, but serological diagnostics is an independent diagnostic method. In accordance with this, we define methods for diagnosing bacterial infections.
Microbiological diagnostics begins with the taking of the test material. Material under study there may be discharge of the patient (feces, urine, sputum, pus, mucosal discharge), biopsy material (blood, cerebrospinal fluid, pieces taken during surgery or tissue examination), autopsy material taken at autopsy. Sometimes objects of the external environment are subjected to microbiological research - water, food, soil, air, material from animals. The taken material is accompanied by a referral to the laboratory, the correct transportation and storage of the test material is ensured.
Table 1.
BASIC METHODS OF MICROBIOLOGICAL DIAGNOSIS
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Microbiology 20.09.96.
The causative agents of SARS (acute respiratory infections)
ARI is caused by many pathogens: there are about 200 of them. Among them are
prokaryotes: bacteria, mycoplasmas, chlamydia. Diagnosis of acute respiratory
Viral infections are put already by the doctor. Therapists are already differentiating
clinical symptoms, what kind of acute respiratory disease is it: viral or bacterial.
Among the causative agents of SARS: influenza viruses, parainfluenza, rhinoviruses,
reoviruses, etc. About 200 ARVI pathogens are known. Only
laboratory method can prove that the disease is caused by a virus
flu, etc. Even during an epidemic, every 10th flu diagnosis is
erroneous, in the non-epidemic period the number of errors reaches 30-40%.
FLU (from the French grippe - to seize, proposed by doctor Sabazh at 19
century). Synonym for the Italian influenza.
The viral nature of influenza was proven in 1933. English scientist
Smith and co-authors isolated a virus from a patient with acute respiratory infections. In our country, two
outstanding scientists A.A. Smorodintsev and L.A. Zilber in 1940 was
isolated another influenza virus that differed from the virus isolated in
1933. In 1974, another influenza virus was discovered. At present
There are 3 known influenza viruses, designated A, B, and C. All those innumerable
the disasters that influenza brings are associated with the influenza A virus. Influenza virus
B also periodically causes rises in incidence, but this is not so.
scary, like epidemics and pandemics caused by the influenza A virus.
The influenza A virus has been studied down to the submolecular level. All viruses
influenza contain RNA, in the center of the virus particles is
ribonucleoprotein, which consists of 8 fragments - 8 genes. 1-6 genes
encode each synthesis of one protein, and 7-8 genes encode 2 proteins each;
a total of 10 proteins encode the genome of the influenza virus. Outside RNP coated
protein shell, and also covered with supercapsids on the outside. Supercapsid
influenza virus consists of a lipoprotein membrane, those cells in which
the virus multiplied (since it leaves the cell by budding).
Interestingly, if different influenza A viruses multiply in different cells
their surfaces can vary considerably. 2 are built into the supercapsid
protein - enzyme. They are embedded in the form of spikes:
hemagglutinin 500-600 spikes. This enzyme has an affinity for
mucoprotein receptors of cells, that is, it reacts with them and the virus
adsorbed on the surface of sensitive cells. Such receptors are
on the surface of erythrocytes. Consequence of adsorption of the virus on erythrocytes
is hemagglutination. Hence the method of indicating the virus: take blood and
add a drop of liquid containing the virus: after 1.5 minutes we observe
whether there is agglutination or not. If the virus-containing liquid is triturated and
add erythrocytes to each dilution, we will determine the amount of virus
A. In the presence of immune sera to known antigens, we
virus-containing fluid is mixed with serum: homologous antibodies
bind to hemagglutinin and inhibition reaction is observed
hemagglutination. It is now known that the influenza virus has
several types of hemagglutinin. Human influenza viruses are known to have 4
antigenic type of hemagglutinin (denoted H). Notable following
antigenic variants: H1 (with antigenic variants 1,2,3), H2 (with
antigenic variants 1,2,3) H3 (with antigenic variants 1,2,3).
neuraminidase between hemagglutinin spikes. Neuraminidase is an enzyme
cleaving neuraminic acid, and it belongs to the group of sialic
acids found in cell membranes. The role of neuraminidase -
participation in the maturation of the cell, but not help in entering and exiting
cells. Human influenza A viruses have 2 antigenic variants of the type
neuraminidase N1 N2.
Outwardly, the virus looks like a sea urchin - it is a spherical formation
somewhere 100 nm in diameter, covered with spines.
Antigenic properties of the influenza A virus.
Influenza viruses have several known antigens: one antigen is
S-antigen, it is associated with a ribonucleoprotein, that is, an internal antigen.
According to the S antigen, influenza viruses are easily divided into influenza A viruses, influenza
B, influenza C. An antigenic crossover is impossible here, since there is
strict antigenic specificity The textbook says that the influenza virus has
there is a V-antigen, but in fact, surface antigens are designated like this:
this includes hemagglutinin and neuraminidase. The following types are known
influenza virus:
influenza A virus with H0N1 antigens
influenza A virus with H1 N1 antigens. Appeared in 1947
circulated for 10 years (until 1957), disappeared for 20 years, reappeared in
1957 and is still in circulation today.
H2 N2 appeared in 1957, circulated for 10 years and disappeared.
H3N2 appeared in 1968 and is still circulating today.
The H0N1 influenza virus was discovered in 1933 and circulated until 1947 and
has disappeared and for 50 years no one has singled it out now.
Thus, the influenza A virus that causes the disease now can
be of 2 types. When these circumstances were clarified, it turned out that
the virus circulated for a while, caused an epidemic and disappeared in 1957,
because a new virus has appeared that distinguishes by 2 antigens and by
hemagglutinin and neuraminidase. It was a pandemic: 2/3 were ill
the population of the earth. This virus disappeared, but in 1968 there was another epidemic.
A new virus has emerged that differs in the H antigen. Thus,
a pattern is found: the emergence of a new virus depends on
development of immunity in humans. The more different the new virus is from
previous, the higher the incidence. This rule gives as
theoretical substantiation of how to act in order to prevent such
rises in morbidity.
Influenza A virus variability. Influenza virus variability is due to
two genetic processes:
a genetic shift occurs as a result of a complete change of a gene and is caused by
gene exchange during simultaneous reproduction of two influenza viruses in a cell
antigenic drift - a change in the antigenic composition, without a complete replacement
antigen. Small changes occur within the antigen. At the core
antigenic drift lie point mutations of the gene, and as a result
antigen changes.
Types of infections. There are three types of infections:
productive infection: the virus is adsorbed, penetrates, reproduces
and exits. The cell is destroyed. If this happens in the body,
then there are serious illnesses.
Asymptomatic infection: the rate of reproduction is low. Cells suffer
less and at the level of the body the disease is asymptomatic, but
the patient is the source of the infection
latent infection: this type of infection has only been studied in
cell cultures in vitro. Has this type of infection occurred in
the human body is not known.
It turns out that after the penetration of the virus, when RNP is released, it
attached to the nucleus of the cell and so exists in the cell. RNP for the cell
alien structure, and the heredity of the cell is conservative, that is
will not tolerate something foreign inside, but, nevertheless, RNP
somehow exists inside the cell. RNP is passed on to cellular progeny.
It is believed that the 20-year failure of the virus is connected precisely with this mechanism.
DISEASES CAUSED BY THE INFLUENZA VIRUS: 2 influenza pandemics are known:
the first is a Spaniard in the 18-20s. of our century, the pandemic in 1957. During
20 million people died from the flu. Influenza virus and causative agents of acute respiratory infections
shorten life expectancy by about 10 years.
Influenza - anthroponosis. Human influenza viruses cause disease only
in humans (there are only reports that an increase in the incidence of influenza
in humans, the incidence of acute respiratory infections in animals increases). The route of infection
airborne. The virus is not stable in the environment.
The gateway of infection is the upper respiratory tract. Influenza viruses have an affinity
to the prismatic epithelium of the upper respiratory tract. When reproduction
cells suffer from minor disturbances to cell necrosis. Speed
reproduction of the virus is very high and in 2-3 hours the population of viruses
increases by several orders of magnitude. Therefore, the incubation period of influenza
short. In the early stages of the disease, changes
degenerative-dystrophic. Inflammation does not occur. If these early
periods develop pneumonia, then it again passes without a bright
inflammatory response. Late bronchitis and pneumonia often develop
with the addition of a bacterial infection. If we examine the sectional
material of people who died from influenza pneumonia, then always
detected by microscopy of staphylococci, so it is like
usually mixed infections.
COMPLICATIONS WITH FLU:
intoxication: temperature 39-40, caused or by the viral
particles or fragments of the virus. Significant changes in the wall of blood vessels
increased permeability (hemorrhage), therefore, in the acute period
bath is contraindicated.
From the side of the central nervous system: due to the action of viral proteins, due to the action
neurotropic viruses.
MECHANISMS OF ANTI-VIRAL PROTECTION. A major role in recovery and protection
from influenza belongs to antibodies against antigens and enzymes of the virus.
Immunity with influenza is tense, type-specific. alpha inhibitors
beta and gamma react with hemagglutinin by the active site and the virus does not
can be adsorbed on the cell. The presence and amount of the inhibitor is included
into the human genotype, being its individual feature. Next
defense mechanism - interferon systems. There are interferons alpha, beta and
gamma. Normally, a person does not have interferons, interferon begins
produced by a cell when it is either infected by a virus or
stimulated by some inductor. Ability to produce
interferon is also incorporated in the human genotype.
LABORATORY DIAGNOSIS.
There are three main methods:
express diagnostics: immunofluorescent method, ELISA. Method
immunofluorescence: polished glass is introduced into the patient's nasal passage
and a light scraping is done. Then the glass is treated with luminescent
sera and if there is a viral antigen in the cell, antibodies will be with it
react and we will see the glow.
Virological. They take a wash from the patient's nasopharynx, infect a chicken
embryo, after incubation, the presence of the virus is checked by reaction
hemagglutination, the virus titer is determined in the inhibition reaction
hemagglutination.
serodiagnosis. The diagnostic criterion is the increase in titer
antibodies. This is a retrospective method.
TREATMENT: One of the most effective treatments for influenza is the use of
anti-influenza sera. These are horse sera obtained by
hyperimmunization with influenza vaccine. The resulting serum is lyophilized
dried, mixed with sulfa drugs and applied
intranasally. May cause an allergic reaction, so now
use anti-influenza gamma globulins. Also used
interferon intranasally, which is especially effective in the initial stage
diseases. Also used drugs that suppress the reproduction of the virus
rimantadine, riboverin, etc.
FLU PREVENTION: Academician Belyakov came to the conclusion that the most
vaccination is reliable. At the moment there are:
live influenza vaccine (developed by Smorodintsev) is administered
intranasally
killed vaccine - contains formalin-treated viruses
subvirion vaccine, contains isolated from viral particles
hemagglutinin.
Synthetic vaccine, contains chemically synthesized
hemagglutinin.
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03 Nov 2009SARS- various acute infectious diseases resulting from damage to the epithelium of the respiratory tract by RNA- and DNA-containing viruses. Usually accompanied by fever, runny nose, cough, sore throat, lacrimation, symptoms of intoxication; may be complicated by tracheitis, bronchitis, pneumonia. Diagnosis of SARS is based on clinical and epidemiological data, confirmed by the results of virological and serological tests. Etiotropic treatment of acute respiratory viral infections includes taking antiviral drugs, symptomatic - the use of antipyretics, expectorants, gargling, instillation of vasoconstrictor drops into the nose, etc.
General information
SARS - airborne infections caused by viral pathogens that affect mainly the respiratory system. SARS are the most common diseases, especially in children. During periods of peak incidence of acute respiratory viral infections, ARVI is diagnosed in 30% of the world's population, respiratory viral infections are many times higher in frequency than other infectious diseases. The highest incidence is typical for children aged 3 to 14 years. An increase in the incidence is noted in the cold season. The prevalence of infection is ubiquitous.
SARS are classified according to the severity of the course: there are mild, moderate and severe forms. The severity of the course is determined based on the severity of catarrhal symptoms, temperature reaction and intoxication.
Causes of SARS
SARS are caused by a variety of viruses belonging to different genera and families. They are united by a pronounced affinity for the cells of the epithelium lining the respiratory tract. SARS can cause various types of influenza viruses, parainfluenza, adenoviruses, rhinoviruses, RSV 2 serovars, reoviruses. The vast majority (with the exception of adenoviruses) pathogens are RNA-containing viruses. Almost all pathogens (except for reo- and adenoviruses) are unstable in the environment, they quickly die when dried, exposed to ultraviolet light, and disinfectants. Sometimes SARS can cause Coxsackie and ECHO viruses.
The source of ARVI is a sick person. The greatest danger is presented by patients in the first week of clinical manifestations. Viruses are transmitted by the aerosol mechanism in most cases by airborne droplets, in rare cases it is possible to implement a contact-household route of infection. The natural susceptibility of humans to respiratory viruses is high, especially in childhood. Immunity after infection is unstable, short-term and type-specific.
Due to the multiplicity and diversity of types and serovars of the pathogen, multiple incidence of acute respiratory viral infections in one person per season is possible. Approximately every 2-3 years influenza pandemics associated with the emergence of a new strain of the virus are recorded. SARS of non-influenza etiology often provoke outbreaks in children's groups. Pathological changes in the epithelium of the respiratory system affected by viruses contribute to a decrease in its protective properties, which can lead to the occurrence of a bacterial infection and the development of complications.
SARS symptoms
Common features of SARS: a relatively short (about a week) incubation period, acute onset, fever, intoxication and catarrhal symptoms.
adenovirus infection
The incubation period for adenovirus infection can range from two to twelve days. Like any respiratory infection, it begins acutely, with a rise in temperature, runny nose and cough. The fever can last up to 6 days, sometimes it runs into two oxen. Symptoms of intoxication are moderate. For adenoviruses, the severity of catarrhal symptoms is characteristic: abundant rhinorrhea, swelling of the nasal mucosa, pharynx, tonsils (often moderately hyperemic, with a fibrinous coating). The cough is wet, sputum is clear, liquid.
There may be an increase and soreness of the lymph nodes of the head and neck, in rare cases - lienal syndrome. The height of the disease is characterized by clinical symptoms of bronchitis, laryngitis, tracheitis. A common symptom of adenovirus infection is catarrhal, follicular, or membranous conjunctivitis, initially, usually unilateral, predominantly of the lower eyelid. In a day or two, the conjunctiva of the second eye may become inflamed. In children under two years of age, abdominal symptoms may occur: diarrhea, abdominal pain (mesenteric lymphopathy).
The course is long, often undulating, due to the spread of the virus and the formation of new foci. Sometimes (especially when serovars 1,2 and 5 are affected by adenoviruses), a long-term carriage is formed (adenoviruses are latently stored in the tonsils).
Respiratory syncytial infection
The incubation period, as a rule, takes from 2 to 7 days; adults and children of the older age group are characterized by a mild course of the type of catarrh or acute bronchitis. Runny nose, pain when swallowing (pharyngitis) may be noted. Fever and intoxication are not typical for a respiratory syncytile infection; subfebrile condition may be noted.
The disease in young children (especially infants) is characterized by a more severe course and deep penetration of the virus (bronchiolitis with a tendency to obstruction). The onset of the disease is gradual, the first manifestation is usually rhinitis with scanty viscous secretions, hyperemia of the pharynx and palatine arches, pharyngitis. The temperature either does not rise, or does not exceed subfebrile numbers. Soon there is a dry obsessive cough like that of whooping cough. At the end of the coughing fit, thick, clear or whitish, viscous sputum is noted.
With the progression of the disease, the infection penetrates into smaller bronchi, bronchioles, the respiratory volume decreases, respiratory failure gradually increases. Dyspnea is mainly expiratory (difficulty exhaling), breathing is noisy, there may be short-term episodes of apnea. On examination, increasing cyanosis is noted, auscultation reveals scattered fine and medium bubbling rales. The disease usually lasts about 10-12 days, in severe cases, an increase in duration, recurrence is possible.
Rhinovirus infection
SARS treatment
ARVI is treated at home, patients are sent to the hospital only in cases of severe course or the development of dangerous complications. The complex of therapeutic measures depends on the course, severity of symptoms. Bed rest is recommended for patients with fever up to the normalization of body temperature. It is advisable to follow a complete, protein-rich and vitamin-rich diet, drink plenty of fluids.
Medicines are mainly prescribed depending on the prevalence of one or another symptomatology: antipyretics (paracetamol and complex preparations containing it), expectorants (bromhexine, ambroxol, marshmallow root extract, etc.), antihistamines for desensitization of the body (chloropyramine). Currently, there are a lot of complex preparations that include active ingredients of all these groups, as well as vitamin C, which helps to increase the body's natural defenses.
Locally with rhinitis, vasoconstrictors are prescribed: naphazoline, xylometazoline, etc. With conjunctivitis, ointments with bromnaphthoquinone, fluorenonylglyoxal are applied to the affected eye. Antibiotic therapy is prescribed only if an associated bacterial infection is detected. Etiotropic treatment of acute respiratory viral infections can be effective only in the early stages of the disease. It involves the introduction of human interferon, anti-influenza gamma globulin, as well as synthetic drugs: rimantadine, oxolinic ointment, ribavirin.
Of the physiotherapeutic methods of treating ARVI, mustard bath, can massage and inhalation are widespread. Supportive vitamin therapy, herbal immunostimulants, adaptogens are recommended for people who have had ARVI.
Forecast and prevention of SARS
The prognosis for SARS is generally favorable. The worsening of the prognosis occurs when complications occur, a more severe course often develops when the body is weakened, in children of the first year of life, in senile people. Some complications (pulmonary edema, encephalopathy, false croup) can be fatal.
Specific prophylaxis consists in the use of interferons in the epidemic focus, vaccination with the most common strains of influenza during seasonal pandemics. For personal protection, it is desirable to use gauze bandages covering the nose and mouth when in contact with patients. Individually, it is also recommended to increase the protective properties of the body as a prevention of viral infections (rational nutrition, hardening, vitamin therapy and the use of adaptogens).
Currently, specific prevention of SARS is not sufficiently effective. Therefore, it is necessary to pay attention to general measures for the prevention of respiratory infectious diseases, especially in children's groups and medical institutions. As measures of general prevention, there are: measures aimed at monitoring compliance with sanitary and hygienic standards, timely identification and isolation of patients, limiting population crowding during epidemics and quarantine measures in outbreaks.
