Where does the influenza virus live? Facts about viruses and bacteria: Basic rules of hygiene. How the flu is transmitted

The influenza virus annually contributes to the infection of hundreds of thousands of people, for a long time knocking them out of their usual rhythm of life, provoking the development of serious complications. Every year, more than 15% of the world's population suffers from its effects. This viral disease is distinguished by the severity of the course and special consequences, which is why it is recognized as the most dangerous among all existing ones.

The causative agent of influenza is a type of acute respiratory viral infections, of which there are more than two hundred. Influenza has a high epidemic significance, therefore it occupies a special place among other infections.

To date, experts have identified more than two thousand varieties of influenza, all of which differ according to their own antigenic structure. Once having transferred one type of disease. the possibility of re-infection with a different strain cannot be ruled out. Even re-infection with the same strain after a few years becomes possible due to the fact that the immune memory is weakened.

Differences in the internal structure of the microorganism allow us to distinguish three of its varieties:

Type A virus: is characterized by high aggressiveness, it is he who provokes the development of rather serious diseases. This virus changes rapidly, it has the ability to infect not only humans, but also animals (pig and bird species are caused precisely by its effect). A person who has had this infection receives immunity, which allows him to avoid re-infection for 1-3 years. It is he who provokes the development of pandemics, affecting both children and adults.
Type B virus: is characterized by minimal aggressiveness, it can provoke the flu, which proceeds quite easily. This variety is not very variable, it only affects humans. Immunity earned by a person can last at least three years, so epidemics caused by its massive spread rarely occur. Outbreaks of a local type are more often recorded, affecting only children, adults get sick much less often.
Type C virus: this strain is practically asymptomatic, it is quite variable, children are most often infected. Cases of the disease are isolated and are determined through virological studies.

In addition to types, influenza subtypes are also noted, they differ in their antigenic structure. Antigens are called proteins that cover the surface of viruses, they are necessary for normal viral activity.

Permanent mutations have led to the formation of different subtypes of influenza:

18 subtypes of hemagglutinin;
11 subtypes of neuraminidase.

What does an influenza virus look like under a microscope? This is a set of cells that scientists are still arguing about, deciding whether to consider them alive or dead. The structure of the influenza virus is primitive, they do not have metabolism, respiratory functions, do not need nutrients.

The size of the influenza virus is small, for reproduction they require the genetic material of the cells on which they are located.

Influenza pathogens contain proteins (hemagglutinin) and enzymes (neuraminidase). The first are necessary for viruses to settle in the human body, the second for penetration into the cells of the respiratory organs, by deceiving the immune system.

How does the influenza virus mutate? By mixing its various subtypes, which leads to the formation of new species.

How is the virus spread?

The causative agent of influenza is a virus that enters the airspace through saliva and secretions from the catarrhal organs of a sick person (spread can occur during sneezing or coughing). The spread of infection can occur at a distance of up to four meters from person to person.

To prevent this process, all sick people should be isolated, if this cannot be achieved, it is necessary to wear a protective mask. It will contain the spread of saliva with viral particles, most importantly, change it to a new one at least every two hours.

Healthy people may not wear masks in order to protect themselves from infection. Once the viral particles have already spread through the air, the mask will not be able to filter them, so the process of wearing them loses its usefulness.

In addition to the above, influenza can have a contact method of spread. Recently, this type of infection transmission is the most frequent, due to the fact that a large number of people live in cities, forced to be close to each other.

Infection occurs as follows: the carrier of the virus coughs or sneezes, while covering the mouth with his own hand, which he then puts on the handrail of public transport, the handle of the shopping cart, the elevator buttons. After the infection has penetrated the skin of a healthy person from these objects, it is enough for him to simply touch the mucous membranes of his mouth, nose, or just his face to become infected.

On the skin, viral particles can remain active for at least 15 hours, all this time, remaining a threat to the body.

Therefore, it is very important to accustom yourself to the fact that outside the home you should not touch your own face, eat anything without first washing your hands with soap. While at school or work, you should periodically clean your hands with wet wipes that have an antibacterial effect. And, returning home, you need to thoroughly wash your hands, as well as clean the nasal cavity with saline solutions.

Does alcohol kill the flu virus? Recent studies by scientists have confirmed the fact that ethyl alcohol can only affect surfaces that are being processed. To overcome the infection that has already penetrated to a person, alcohol cannot.

At what temperature does the influenza virus die? How long does it live in the human body, in the air, things? To protect yourself from a possible disease, you need to understand all these issues.

How long does the virus live in the human body?

How long does a virus live in the human body? The virus can be in the cells of the human body long before it begins its active life. This period, called the incubation period, can last from several hours to 7 days. It depends on the state of human health, the presence of chronic diseases, the strength of immunity and a number of other factors.

The incubation period is the time when the virus does not just doze, but multiplies, increasing its own population, releasing toxins, which provoke intoxication. During this period, the subject is already contagious to the people around him.

The causative agent of the disease, not having a cellular structure, cannot independently produce substances that are necessary for its development and reproduction. It can get inside the cells, causing them to reproduce the viral population. After performing this function, the cell simply dies, new sources of infection, toxins formed during the process, are released. Next, cells located in the neighborhood are infected, which contributes to an avalanche-like increase in the process.

The entire period of viral activity inside the cells of the body, a person is contagious to his own environment. It spreads the infection especially actively during the first three days of the disease.

A mild course of the disease allows a person to recover after a week. If we are talking about a complex disease process, then a person can remain contagious for at least two weeks.

Influenza is active for the first seven days of the incubation period, as well as the next 14 days - until the person is on the mend. The pathogen can live in the human body for up to three weeks.

How long does the virus live indoors?

How long does the influenza virus live indoors? Having penetrated into a room with an air temperature of 20-22 degrees, the flu pathogen can remain active for several hours. Low air temperature (about 4 degrees), observed in the refrigerator, can protect the virus from death for a week. Therefore, food that is not eaten by the sick must be disposed of, it cannot be stored and, subsequently, eaten up.

At what temperature does the flu virus die? The resistance of this infection increases when not the temperature changes, but the level of air humidity decreases. It is important to keep this indicator at 70%, turn on the humidifier, cover the heating systems with wet towels, and arrange containers filled with water around the room.

Constant ventilation of the room, carried out several times a day, for 15-20 minutes, allows you to lower the air temperature and drive the virus out of the apartment.

The pathogen is sensitive to solutions used to disinfect surfaces. Wet cleaning, when a sick person is in the apartment, is carried out twice a day. The use of a vacuum cleaner, on the other hand, is not recommended. This unit sucks the viral particles inward, from where, after a while, during cleaning, they can break free again.

An ultraviolet lamp is used to disinfect the room.

How long does the flu virus live on things?

The pathogen can settle not only on the surfaces and mucous membranes of a person, it is able to live up to 10 days on dishes and other objects. If we are talking about tissues, there it can retain its activity for 1-2 days longer.

Therefore, it is important to allocate individual cutlery, towels, bedding and other items to a sick person to maintain personal hygiene. These items should be washed and laundered separately. The flu virus dies at a temperature of 60 degrees, so you need to wash in hot water, and wash the dishes in the dishwasher, or pour boiling water over (the latter option is not always effective, exposure to hot water should last at least 10 minutes).

Do not put the things of the sick person and the rest of the family in the same closet or just put them next to each other. They should be washed separately, in compliance with the temperature regime indicated above.

How long does a virus live in the environment?

How long does the flu virus live in the air? Outside the human body, in the external environment, the pathogen can maintain its activity for a long time. Specific dates depend on what air temperature and humidity indicators are observed at a particular moment.

Even a temperature of -70 degrees is not able to destroy this pathogenic microorganism.

How to avoid getting infected with the virus?

The strain of the influenza virus is highly spread among people, in order to reduce the likelihood of infection, the following recommendations should be followed:

less to be in crowded places, especially during the season when the incidence of influenza increases;
actively walk on the street, spending time on walks, and not indoors;
choose clothes according to the weather in order to prevent a situation where the body is exposed to hypothermia;
avoid riding in transport where a lot of people gather, preferring to walk;
wash hands with soap, rinse the nasal mucosa with saline or saline after returning home;
do not touch the eyes, nose and, in general, the face, while outside the home;
organize cool, humidified air in the apartment, preventing the mucosa from drying out;
eat well;
avoid stressful influence;
rest and sleep;
take multivitamin complexes.

Infection with the flu, being among a large number of people, is quite difficult to avoid. In order to protect your own body from this serious disease, you should follow preventive recommendations, do not give up playing sports and active pastime in the fresh air.

website- However, less than 1% of the bacteria in the human body can cause disease, while others help to perform important functions. For example, the bacteria Lactobacillus acidophilus, which are used in the manufacture of fermented milk products, help digest food and fight harmful microbes.

The microbes inside our body make up the microbiome - the collection of organisms that live in us and interact with each other and us.

As for viruses, according to scientists, some of them do not affect us in any way, but it is possible that they are built into DNA. This means that we have a symbiosis with them, just like with bacteria.

The complex interconnected work of the human body with microorganisms forms immunity to various pathogenic bacteria and viruses. In other words, this is a kind of "grafting" of evolution, which ensures the resistance of the organism to external adverse factors.

But despite this, you should not rely on the steadfastness of your immunity and abuse the rules of hygiene, as well as get carried away with the constant disinfection of yourself and space. For a healthy person, excessive hygiene can even be harmful, because the immune system, freed from the need for constant struggle with microbes, begins to weaken.

Any immunity has its weaknesses - mucous membranes: mouth, nose, genitals, inner surfaces of the eyelids and auditory canals and damaged skin. Therefore, awareness in this area will protect both from infections and from unnecessary fears.

So, despite the differences, the ways of spreading viruses and bacteria are approximately the same: airborne droplets (coughing, sneezing), from skin to skin (when touched and shaking hands), from skin to food (when touching food with dirty hands, viruses and bacteria can enter the intestines), through body fluids (blood, semen and saliva). Sexually or through a dirty syringe, the causative agents of HIV and herpes are most actively spread.

How long do bacteria and viruses live outside the human body?

It all depends on the type of bacteria or virus, and on the surface on which they are located. Most pathogenic bacteria, viruses, and fungi require moist conditions to live, so how long they can live outside the body depends on the humidity of the air.

For example, cold viruses can live on indoor surfaces for over seven days. Generally speaking, viruses live longer on smooth (water resistant) surfaces. However, their ability to cause disease begins to decline after 24 hours.

On the surface of the hands, most cold viruses live much less. Some of them die after a few minutes, but 40% of common cold pathogens are still contagious after being on the hands for an hour.

Like cold viruses, flu viruses live much less on the hands. After the influenza virus has been on the hands of a person for five minutes, its concentration decreases sharply. Influenza viruses can live on hard surfaces for 24 hours, while influenza viruses live on tissue for only 15 minutes.

Influenza viruses can live in droplets of moisture flying in the air for several hours, and even longer in low temperatures.

Intestinal infections can be caused by a variety of microorganisms, including bacteria such as E. coli, Salmonella, C. difficile, and Campylobacter, as well as viruses such as norovirus and rotavirus.

Salmonella and Campylobacter can live for approximately 1-4 hours on hard surfaces and tissues, while norovirus and C. difficile can live much longer.

salmonella bacterium

To prevent the spread of an intestinal infection, wash your hands regularly and thoroughly, especially after going to the toilet. It is also necessary to monitor food hygiene.

Staphylococcus aureus can live on surfaces for several days or even weeks, and this can last even longer than some bacteria and viruses live in general.

Herpes viruses can live for four hours on plastic, three hours on fabric, and two hours on skin. If you have herpetic fever, do not touch the blisters. If you do touch them, for example to apply a cold sore cream, be sure to wash your hands immediately afterwards.

The causative agent of syphilis outside the human body quickly dies when dried, under the action of disinfectants. In a humid environment lives for several hours, is not sensitive to low temperatures.

Fears of HIV infection through the bites of mosquitoes, lice, fleas, bedbugs and other blood-sucking insects are a delusion. In medical practice, there are no cases of human infection with them. Why this does not happen, it is still difficult to give an exact answer. There is a possibility that in the organisms of these creatures there are substances that destroy HIV.

Influenza virus is a representative of RNA-containing viruses from the family of orthomyxoviruses, causing acute damage to various parts of the respiratory tract. Transmitted by airborne droplets and contact. An infectious agent is capable of causing pandemics, and given the possibility of a severe course and the development of complications, it is not surprising that many are interested not only in the route of transmission and clinical manifestations.

How long does the influenza virus live in the air, on clothes, in a person? How long does the flu virus last indoors? What can be done to reduce the chance of infection?

The information provided will help answer these and other questions.

Influenza virus and its lifetime

How long the influenza virus lives outside the body, in the external environment depends on the temperature and humidity of the surrounding air.

Despite the fact that at sub-zero temperatures, the influenza virus lives for years, and at -70 it not only lives, but also retains its virulence (the ability to infect), in general, it is not very stable.

How does the pathogen spread?

It enters the air along with a suspension of saliva and catarrhal secretions, which are thrown out when sneezing and coughing. The infection spreads over a distance of up to 3.5 meters. If it is not possible to isolate the patient, he needs to wear a mask that would trap drops of mucus and saliva, change the mask every 2-3 hours.

The mask is unable to filter the pathogen that has already entered the air - its pores are too large for this. Therefore, it is irrational to wear it to healthy people for preventive purposes.

Another way the flu spreads is through contact.. Previously, not too much attention was paid to it, but in recent years this transmission route has become more and more relevant, especially in the city, with a large population density. The infection enters the patient's skin when sneezing and coughing, if he covers his mouth with his hand, after he wipes his nose with his fingers, or blows his nose not into a handkerchief. Further, drops of mucus and saliva remaining on the hands, together with the viral particles contained in them, which remain active on the skin for up to 15 hours, fall on any objects that the sick person touches.

Handrails in public transport, basket and cart handles in supermarkets, money, door handles in the office - this is where the flu virus lives during an epidemic, maintaining virulence up to two days on plastic and metal objects. From these objects, particles of biological fluids, along with the source of infection, are transferred to the skin of other people, for whom it is enough to scratch their nose, rub their eyes, eat something with their hands (bread, cookies, etc.), so that the infection gets on the mucous membranes of the respiratory tract and begins develop. “Conscious” people who do not want to become a source of infection can sneeze and cough into the crook of the elbow, it is advisable to teach children to do the same.

To protect yourself from the contact route of transmission of the pathogen, it is recommended not only to wash your hands, but also to use antiseptic wipes or gels during the day. This is especially true for children who regularly lick their fingers, bite their nails, etc. About how long the influenza virus lives on objects, outside of a person, will be discussed in more detail later.

Influenza indoors

How long does the influenza virus live indoors?

Or how long does the flu virus stay in an apartment?

Several hours at a temperature of 22 degrees.

But in the refrigerator, where the temperature is usually maintained at about +4 degrees, it can remain viable for a week. Therefore, it is not necessary to store unfinished food in the refrigerator.

The stability of the pathogen increases as the air humidity decreases. When dried, it can be stored for several days. That is why the air in the room in which the patient is located must be moistened: turn on a special device, hang wet sheets, terry towels on radiators, arrange vessels with water. The room itself needs to be ventilated - just ventilate, and not slightly open the window - every two to three hours for at least half an hour. Such ventilation reduces the concentration of the infectious agent in the air by 80-90%.

The causative agent is sensitive to the action of disinfectant solutions, so it is necessary to do wet cleaning twice a day with their use. But vacuuming, on the contrary, is not recommended: most of the filters used in the vacuum cleaner do not trap viruses, while the air stream emanating from them again disperses the infection in the air.

If the house has an ultraviolet lamp, it is ideal for disinfecting the room.

Virus under the microscope

How long does the flu virus live on things?

On items such as dishes, the infectious agent lives up to 10 days. On fabric: towels, handkerchiefs - the infection can persist for up to 11 days.

The patient needs to have separate dishes. It also needs to be washed separately. If the family uses a dishwasher, choose a mode in which the water is heated to a temperature of at least 60 degrees. At this temperature, the maximum duration of the influenza virus is 10 minutes.

The patient should have a separate towel, which should be kept in his room. In the same way, you can’t put his clothes, handkerchiefs, bed linen with the things of other family members. You can wash things together with all things at a temperature of 60 degrees, but if the composition of the fabric does not allow this, the items must be washed separately.

Summary

Thus, the stability of the influenza virus in the external environment is low. How long does the influenza virus live outside the body: in the air, on things, depends on:

on ambient temperature: the higher, the shorter the life, at room temperature - a few hours;
from air humidity - in a dried form, in dust, lives longer;
from the presence of ultraviolet sources: under UV rays it dies instantly.
from the surface material: on paper up to 12 hours, on metal or plastic up to 2 days, on glass up to 10 days, on fabric up to 11.
on the skin, the pathogen persists for up to 15 hours.

How long does the influenza virus live in the human body

You need to start with the question of how long the influenza virus lives in the body - in humans - before the first clinical manifestations of the disease appear. The incubation period of the disease can last from several hours to a week. All this time, the infection not only lives, but also actively multiplies in the epithelial cells of the respiratory tract, so a person becomes contagious already at this time.

Like all viruses, the pathogen itself does not have a cellular structure and is incapable of synthesizing the substances it needs for existence, especially to reproduce on its own. Therefore, it penetrates into the cell, integrates into its structures, and the cell begins to synthesize new viruses. Having fulfilled its function, the cell dies, releasing "to freedom" both new sources of infection and toxic substances formed in the process of synthesis. Neighboring cells become infected, and then the process grows like an avalanche.

The disease begins acutely: the state of health is rapidly deteriorating, weakness, dizziness, headache appear, the temperature rises rapidly to 39-40 and above, blood pressure drops. The patient can indicate the time of the disease with an accuracy of literally up to an hour. This feature of the course of the disease gave it its name (in French, grippe means "grab, squeeze"). There are pains in the muscles of the limbs, lower back, aches when moving the eyeballs.

Damage to the epithelium of the trachea leads to a painful cough without discharge. It is characteristic that in the first 2-3 days of the disease there is neither a runny nose as such, only nasal congestion is noted, nor sputum when coughing. That is why the doctors of the old school called this disease "dry catarrh" (catarrhal inflammation - inflammation with mucous discharge). By the time nasal discharge appears, the temperature has already dropped to subfebrile numbers, in mild cases of the disease it disappears completely. A second round of fever or a prolonged course of it may mean the appearance of bacterial complications.

During the illness, the permeability of blood vessels increases, which can manifest itself as nosebleeds, as well as hemorrhages under the wall of the mucous membrane (“raspberry trachea”), the development of hemorrhagic pneumonia (caused by bleeding into the alveoli). Therefore, with influenza, in no case should you “knock down” the temperature with aspirin or any combined means based on acetylsalicylic acid, which reduces blood clotting. This increases the likelihood of developing hemorrhagic pulmonary edema.

All this time, the patient actively releases the infectious agent into the environment. It is especially contagious in the first three days of illness.

With a mild course of the disease, the symptoms disappear in 7-12 days. Isolation of the virus usually continues for a week. With a complicated course of influenza, the patient remains contagious for up to two weeks from the onset of the disease.

Thus, how many days does the influenza virus live in the human body:

incubation period - up to 7 days;
during illness - up to 14 days.

Therefore, the lifespan of the influenza virus is up to 21 days.

How to avoid infection

First of all, during the epidemic, it is necessary to limit contact with people as much as possible. Of course, this does not mean that you need to stop going to work or school. But it is better to postpone visiting entertainment events: cinema, concerts, performances until the end of the epidemic. You should also not use shopping centers as a place for recreational activities, it is better to change them to open skating rinks, a ski track or a regular walk. Despite how long the flu virus lives at low temperatures, its concentration in the outdoor air is almost zero. The main thing is not to overcool.

If the place of work or study is not too far, it is better to dress for the weather and get there on foot, instead of picking up the infection on public transport. In addition, an active walk will help strengthen the immune and cardiovascular systems.
For your own peace of mind, you can use a mask in transport and at work, but it only becomes effective for preventing infection when worn by the patient. Although it is best to convince a colleague to go on sick leave.
You need to unlearn the habit of touching your face with your hands, rubbing your nose, eyes. After transport, shopping, before eating, be sure to wash your hands, or, if this is not possible, treat them with an antiseptic gel.
After returning home, you can rinse your nose with saline or special aerosols. This will not only mechanically remove some of the infectious agents from the mucous membrane, but also moisturize it.
Both the home and workplace must be ventilated to reduce the concentration of the virus in the room.
In order for the mucous membrane to fully perform its protective functions, it is necessary to constantly humidify the air in the room, preventing the formation of dry crusts in the nose.
The general condition of the body can improve good nutrition, adherence to the daily regimen, and the intake of multivitamin complexes.

conclusions

How long the influenza virus lives indoors, remains on objects, will depend on the temperature and humidity of the air, as well as the surface material. A person becomes contagious from the beginning of the incubation period until the end of the disease, which in the worst case can be three weeks from the moment of infection.

To prevent infection, it is necessary to observe the daily routine, avoiding overwork, to be in the fresh air more often, avoiding large crowds of people, to carefully pay attention to personal hygiene and the hygiene of the premises in which you have to stay.

Additional strengthening of the body's defenses can be facilitated by dosed physical activity, proper nutrition, and, if necessary, the intake of vitamin and mineral complexes.

Students in grades 8-10

Smirnova M.A.

Research topic

flu virus

problem question

Where does the flu virus live?

Research hypothesis

Influenza virus can only live in living organisms

Research objectives

Find out where the flu virus is located

Learn how to fight the flu

What to do for prevention

Results

Influenza refers to acute infectious diseases and most often occurs in the form of outbreaks and epidemics. These epidemics tend to start suddenly and spread very quickly. They happen almost every year. The epidemic can last from 1 to 3 months. At the same time, from 5 to 20% of the population falls ill. Therefore, the flu accounts for the largest number of cases of all diseases that occur in humans. Accordingly, the number of deaths associated with influenza is the largest.

Cause of influenza virus

How the influenza virus is transmitted

The source of infection is always a person with influenza. It is most contagious from the first hours of the disease until the 3-5th day of illness. Infection occurs by flying viruses with droplets of mucus when talking, coughing, sneezing. At these moments, for a short period of time, an infection zone with a radius of 2-3 m is formed around the patient. When the smallest drops of saliva, mucus, sputum containing viruses are inhaled, healthy people become infected. In addition, transmission of the virus through hands, toys, care items is possible.

The manifestation of the disease

Major influenza epidemics or pandemics occur at intervals of 10-12 years. Simple influenza epidemics caused by influenza A virus occur approximately every 2-3 years, influenza type B - every 4-6 years. Type C is not characterized by epidemics, but small outbreaks can occur in children and debilitated people. Influenza usually occurs in autumn and winter. The disease develops most often after 12-48 hours from the moment of contact with the sick person. But this period can be reduced to a few hours or lengthened up to 3 days. Most often, the flu starts suddenly. Body temperature rises rapidly and remains at a high level for 3-5 days. Periodically there are chills, weakness, sweating, headache, body aches, pain in muscles, joints, eyes, fear of bright light and lacrimation. At the same time, a dry cough, sore throat, hoarseness, nasal congestion and runny nose appear. Vomiting and even stool disorders may occur.

Influenza is dangerous for its complications, although the frequency of their occurrence is relatively low. Pneumonia occurs most often, but there may also be otitis media, sinusitis, meningitis, encephalitis, neuritis, myocarditis, Reye's syndrome, and toxic shock. After the disease, immunity is formed only to a certain type of virus, which was the causative agent of this particular disease. Thus, a person who has just recovered from influenza caused by type A may again get the flu, but already caused by type B or C.

Disease history

The flu has been known for a long time. The first mention of such a disease was as early as 412 BC. e. Hippocrates also described a similar disease. Outbreaks of a similar infection were noted in 1173. The outdated name for influenza is influenza. According to one version, it appeared in the middle of the 15th century. after the epidemic, the cause of which is associated with the influence of the stars (influence). According to another version, the name of the disease comes from the Latin "influere" - to invade. Thirdly - from the Italian "influenza di freddo" - a consequence of cooling. The modern name for influenza comes from the Dutch "griep". This word is used in conversation in a similar way to the English "flu". The ancestor of the latter is the French "gripper". It also serves as a collective concept that combines a large number of acute respiratory infections caused by various viruses. Throughout the history of mankind, there are about twelve major epidemics and pandemics of influenza. The most severe of these was the "Spanish flu" pandemic, which is popularly called the "Spanish Flu". Among all medical disasters, it is second only to the plague of the XIV century. The pandemic lasted from 1918 to 1920. During it, about 21 million people died and 500 million fell ill. Influenza then developed extremely quickly. A person was relatively healthy in the morning, fell ill by noon, and could die at night. In Spain itself, which was the first to encounter the disease, 39% of the population had been ill. In many European countries, public institutions (schools, churches, courts, theaters) did not work during the year, sellers forbade buyers to enter the store. A feature of the infection was the defeat of predominantly young people, while usually the flu is dangerous for children and the elderly.

Influenza virus vaccines

For influenza vaccination, live and inactivated vaccines are used. To date, live vaccines are produced in a small number of countries, such as Russia and China.

Three types of live vaccines are produced in Russia:

purified live vaccine for adolescents over 16 years of age and adults;

allantoic intranasal vaccine for children from 3 to 14 years;

allantoic intranasal vaccine for children from 7 years old, adolescents and adults.

Pathogenesis

With a certain degree of conventionality, the pathogenesis of influenza can be represented as successive phases: the penetration and reproduction of the virus in the epithelial cells of the respiratory tract, the release of the virus, the destruction of the affected cells, the development of catarrhal syndrome, viremia, toxemia, convalescence, the formation of immunity.

Penetration and reproduction of the virus in the epithelial cells of the respiratory tract

Being in droplets of mucus, the virus is drawn into the air stream into the respiratory tract. The higher the dispersion of the mucus aerosol formed during coughing and sneezing of patients, the deeper the virus penetrates into the respiratory tract of a healthy person. It has been experimentally established that the lower respiratory tract is much more sensitive to the influenza virus than the upper ones. The main target of the virus is the cells of the cylindrical ciliated epithelium. In order for infection to take place, the virus must overcome nonspecific airway resistance factors. These include the viscous properties of mucus, the constant movement of the cilia of the cylindrical epithelium, non-specific inhibitors of virus replication contained in the mucus of the respiratory tract, macrophages that capture the virus and thus suspend its action, secretory IgA. In addition, after the penetration of the first viral particles into the cells, these cells produce and release interferon into the intercellular fluid, the main task of which is to protect the cells that have not yet been infected from the penetration of the virus into them.

If the virus still manages to overcome all obstacles, it attaches with the help of hemagglutinin to the receptors of target cells (in this case, to the ciliated columnar epithelium) and penetrates into the cell, where the virus is “undressed” (“virus striptease”) and the intracellular replication cycle begins, which proceeds at a tremendous speed: already after 4-6 hours a batch of new viruses is created in the cell, which is “pushed” out of the cell through the pores of the membrane. After 24 hours, the number of viruses whose precursor has entered the cell can reach several hundred million. It is this speed of virus replication and its accumulation that explains the very short incubation period - from several hours to 2-3 days.

Virus release, destruction of affected cells

The immediate precursor of the virus envelope is the host cell membrane, so the final formation of viral particles occurs on the cell surface. An important role in the release of the virus is played by neuraminidase, which prevents the aggregation of progeny virions. The released virions infect neighboring cells, some of the viruses penetrate into the blood. The affected cells left behind by the virus lose their oblong shape, become rounded, their nucleus shrinks and fragments. Vacuolization of the cytoplasm occurs with the appearance of basophilic and oxyphilic inclusions in it, cilia are lost. The subsequent death of these cells is due not so much to the cytopathogenic effect of the influenza virus as to the inability of the cell to fully recover after the active consumption of its resources during the synthesis of all components of the viral nucleocapsid in the cell. The fact that the influenza virus leaves the cell without destroying it, and cell death occurs later, within 3-24 hours, explains some delay of the catarrhal syndrome in relation to toxicosis.

Development of catarrhal syndrome, viremia, toxemia

The onset of viremia and toxemia corresponds to the 1st day (hour) of illness (chills, fever). Simultaneously, necrosis and desquamation of the airway epithelium occur. Often large areas of the mucous membrane are exposed, becoming relatively defenseless against bacteria. Areas of extensive desquamation of the epithelium lead to exposure of the submucosal layer. Various irritants - the flow of air passing through the respiratory tract, the exfoliated epithelium - cause irritation of the nerve endings and a reflex dry cough, which can become painful, accompanied by a burning sensation after work. At this time, edema, plethora, and cell infiltration develop in the deeper layers of the airway wall. With the layering of the bacterial flora, purulent-necrotic tracheobronchitis may develop.

The nature of lung damage in influenza is debated to date. Some authors continue to argue about the possibility of developing primary viral pneumonia, considering “hemorrhagic influenza pneumonia” to be especially characteristic. Most pathologists and clinicians disagree with this. Changes in the lungs are regarded by them as a consequence of severe vascular disorders, which it is logical to call toxic hemorrhagic pulmonary edema.

Often, secondary bacterial microflora superimposes on changes in the lungs caused by the influenza virus, which significantly aggravates the course of the disease.

In the blood, the virus can be found both in a freely circulating form and in the form of virus-antibody complexes. In addition to viral particles, decay products of epithelial cells that enter the blood also have toxic properties. Severe toxicosis in influenza is an essential feature of the pathogenesis that distinguishes it from many other respiratory viral infections. The virus has a toxic effect on the vascular and nervous systems, and the severity of lesions is proportional to the degree of toxicosis. The permeability and fragility of blood vessels are significantly increased, which, in combination with microcirculation disorders, can lead to the development of hemorrhagic syndrome. In the occurrence of circulatory disorders, in addition to a direct effect on the vascular wall, the neurotropism of the virus is of great importance. Phase lesions of the autonomic nervous system are characteristic, affecting both its parts (sympathetic and parasympathetic): hypertension is replaced by hypotension, tachycardia - bradycardia, increased secretion of mucus in the respiratory tract, sweating appears.

Changes in the internal organs are of the same type, they are due to generalized vasodilation. With a rapidly developing massive viremia in the first hours of the disease, an infectious-toxic shock may occur with the development of cardiovascular insufficiency. It is based on several factors: vascular (the direct effect of the virus on blood vessels with an increase in their permeability, vasodilation), hemorrhagic syndrome with damage to the adrenal glands and hormone deficiency, and impaired myocardial function. In such patients, death can occur in the next few hours from the onset of the disease.

As a result of toxic damage to the vascular apparatus of the central nervous system, hypersecretion of cerebrospinal fluid occurs, liquorodynamics is disturbed, which leads to an increase in intracranial pressure, cerebral edema may occur. Most often, however, the pia mater, choroid plexus, where influenza virus antigens can be detected, are affected. Currently, the possibility of long-term persistence of the influenza virus in the central nervous system as a slow infection with the subsequent development of such a pathological condition as parkinsonism is not excluded.

Partially, the virus is excreted from the body by the kidneys, which, perhaps, determines the fact that a significant amount of the virus antigen is detected in the epithelium of the distal tubules, as well as in the endothelium of the glomerular capillaries. The kidneys also secrete immune complexes, cell fragments, which leads to sensitization of kidney tissues and subsequently, several weeks and even months after the disease, can cause glomerulonephritis. Even a factor that does not have an antigenic nature (for example, hypothermia) can have a resolving effect in this case.

An infectious-allergic process after an influenza infection can also occur in the endocardium. Changes in the myocardium, determined by the ECG as myocardial dystrophy, are due to toxicosis and circulatory disorders.

Edema, focal hemorrhages occur in the liver, but usually influenza is not accompanied by jaundice, cytolytic syndrome, marked enlargement of the liver, signs of liver failure. However, after suffering influenza type A, more often in children, Reye's syndrome can develop - acute encephalopathy and fatty degeneration of the liver. The pathogenesis of this syndrome is not well understood.

Influenza marked inhibition of cellular immunity. The most pronounced decrease in the number of T-lymphocytes was observed in those cases when the disease was caused by a new subtype of the A virus, which differed in hemagglutinin and neuraminidase from the viruses that the diseased had previously encountered. Complete recovery of the T-lymphocyte population is observed no earlier than 4 weeks from the onset of the disease. With influenza, the phagocytic activity of neutrophils is also sharply reduced. Immunosuppression that develops with influenza makes it possible for bacterial complications to join, activation of foci of infection dormant in the body.

Reconvalescence, the formation of immunity

Since antiviral antibodies begin to be determined in the serum of patients only by the end of the 1st week of illness, it is clear that they cannot participate in the mechanism of recovery. However, it should be noted that the disease proceeds more easily if the serum of the infected contains antibodies (after previous influenza illnesses) against those antigenic determinants of the virus that remained unchanged during antigenic drift. If infection with a virus with a set of antigens unfamiliar to the body occurs, recovery is possible due to non-specific protection factors and the “turning on” of cellular immunity.

Of the previously mentioned factors of nonspecific resistance in antiviral protection, the main role is assigned to interferon, which prevents the reproduction of the virus in the epithelium of the respiratory tract. An important protective reaction of the body is an increase in body temperature. It stimulates phagocytosis, interferon formation, contributes to the acidification of body fluids, and has a direct inhibitory effect on the reproduction of the virus.

In the last 10–20 years, a number of new data on cellular immunity and its role in antiviral defense have been obtained. One of the main factors of cellular anti-influenza immunity are T-lymphocytes. The formation of cytotoxic T-lymphocytes (killers) is the most important link in the mechanism of recovery. T-killers lyse target cells affected by the virus, and immune

T-killers distinguish only types of influenza viruses, but not subtypes, which allows them to have a cross-protective effect. They also secrete lymphokines and activate macrophages. T-helpers interact with macrophages and p-lymphocytes, stimulating antibody production.

Secretory IgA antibodies play an important role in the inactivation of the influenza virus. A large number of them are formed in the respiratory tract, but they are determined in low titers, because. are permanently eliminated by swallowing. It is assumed that the production rate of secretory antibodies is higher than that of serum antibodies. These antibodies are also important from an epidemiological point of view, as they limit the spread of the virus by an infected person.

Along with the destruction of the pathogen, there is a reparative process in the mucous membrane of the respiratory tract, which begins even against the background of the disease: after a few days from the onset of the disease, signs of regeneration of the epithelium are found. These new cells are immune to the virus circulating in the body. Within 1 week, the body is freed from infection, the person recovers. And the resulting antibodies protect it from re-infection with the same virus.

conclusions

Treatment of patients with influenza with moderate and mild course is carried out at home. Only patients with a severe course are subject to hospitalization. The presence of at least one of such signs as hyperthermia (40-41 ° C and above), meningeal syndrome, vomiting, convulsions, shortness of breath, cyanosis, arrhythmia, hypotension in a patient requires unconditional hospitalization. Hospitalization is also carried out according to epidemiological indications (accommodation in hostels, hotels).

The patient is prescribed bed rest during the entire febrile period (it is necessary to remember the possibility of collapse) and rich in vitamins, easily digestible, varied food with sufficient fluid. The room in which the patient is located must be regularly ventilated, while avoiding hypothermia, because. how it can increase coughing and even lead to bronchospasm.

Flu Prevention

Non-specific seasonal prophylaxis includes a number of means and methods for increasing the body's resistance to influenza and other ARVI pathogens. They recommend hardening procedures (gargling with cool water, walking barefoot, sleeping in the cold season with the window open). Use multivitamin preparations "Dekamevit", "Gexavit", "Undevit" 1 tablet 2-3 times a day; Eleutherococcus extract, which has a tonic and tonic properties, increases the body's nonspecific resistance. Apply it 20-40 drops per reception 2-3 times a day for 25-30 days. Prodigiosan is also recommended. It stimulates the T-system of immunity, interferon production, nonspecific resistance factors. Apply a 0.005% solution intranasally with a spray dispenser.

Specific prophylaxis of influenza consists in carrying out vaccination - a mass and effective method of combating influenza. Currently used vaccines are divided into inactivated and live. Inactivated vaccines can be whole-virion and split (consisting of the products of the breakdown of viral particles with the help of detergents). Inactivated influenza vaccines are administered parenterally, so they mainly induce humoral immunity. Since 1989, the use of needleless injectors has been banned due to the risk of HIV transmission. Live allantoic vaccines are administered into the nasal passages with a spray dispenser. They compare favorably with inactivated ones in that, in addition to humoral, they also stimulate local immunity of the respiratory tract (secretory antibodies, cellular immunity). Live vaccines are recommended to be used primarily in small groups and for immunization of children, inactivated ones - in large groups at large enterprises. There is no need for general vaccination. First of all, the vaccine should be administered to persons with an increased risk of complications (elderly people with chronic inflammatory, metabolic, hematological diseases, severe neurological pathology, etc.). But it should be remembered that the vaccine is effective only against a certain type