The mechanism of transmission of influenza and its prevention: how not to get infected on the street

Published: 11/15/2016 17:36

1. How to protect yourself from influenza and ARVI - basic methods
2. Vaccination against influenza and ARVI
3. Varieties of influenza
4. How effective is vaccination?
5. Maintaining good hygiene as flu prevention
6. Transmission mechanism

Influenza is a viral disease that is easy to catch, but getting rid of it, especially if treatment was started late, is not so easy.

Influenza is fraught with numerous complications that can become chronic. Therefore, prevention of acute respiratory infections and influenza is necessary.

Some believe that preventive measures consist of limiting contact with a patient with ARVI and using an antiviral mask on the street and in public places during a flu epidemic.

However, this is not enough, especially if there is a risk of contracting chicken or swine flu. How to protect yourself from influenza or ARVI using folk remedies and medications, recommendations and videos are below.

Why do you need to get tested for influenza?

Specific diagnostics are necessary to identify and study new strains of viruses, the speed of their spread, mutation, to predict the epidemiological situation in the regions, and improve the quality of treatment. Without it, patients are not justified in prescribing truly effective antiviral medications: oseltamivir and zanamivir. They suppress the activity of strains A, the most common type. But they have almost no effect on serotypes B and C. In addition, weakened immunity often provokes the addition of secondary bacterial infections that require additional use of antibiotics.

Prescribing medications blindly delays the time during which the patient could have received other help. For these reasons, several fundamentally different types of diagnostics have been developed.

How to protect yourself from influenza and ARVI - basic methods

Flu and its prevention is an important public issue that concerns everyone. There are three main ways to protect yourself from the flu during its epidemic.

Vaccination. The flu shot is not mandatory, but it can be done if desired at local clinics or private offices.
Prevention of influenza using medications and vitamins.
Prevention of influenza with folk remedies and personal hygiene.

It is worth considering each of the methods in detail to determine whether and how it is possible to protect against the flu as reliably and safely as possible while on the street, in transport, or in contact with a patient with ARVI.

Vaccination against influenza and ARVI

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Vaccination against influenza or ARVI is the most reliable way to protect yourself from a dangerous disease during its epidemic. The vaccine helps strengthen a person’s natural immunity and protects him from both influenza and ARVI of any nature. Vaccinations save the population from such terrible diseases as measles, diphtheria, polio, and tetanus.

Thanks to compulsory vaccination, which is carried out in childhood, these diseases are practically not found in our region today.

The vaccine is not a treatment; it does not destroy the influenza virus itself. This is not a guarantee that a person will never get sick with regular or swine flu. But it will be much easier for him to bear it, without complications and side effects.

The Ministry of Health recommends such preventive measures for ARVI and influenza to be carried out during the cold season, when viruses are especially active - from October to December.

Children can be vaccinated against influenza starting at 6 months of age. It is recommended for people working in public places and institutions, elderly people (over 50 years old), and patients with chronic diseases.

Pregnant women are also at risk. But they can be vaccinated only after examination, in the absence of contraindications, after the first trimester of pregnancy. Vaccination is necessary for schoolchildren, students and military personnel living in barracks.

To get complete information about influenza, to find out the mechanism of infection with it, how specific and necessarily non-specific prevention of influenza is carried out, we invite you to watch the video.

Inconvenient questions about the flu, or Everything you need to know to avoid getting sick

It is a rare person who has not personally experienced the flu. However, even such lucky people have at least heard and know something about this very dangerous disease. How correct are our ideas about a seemingly very common infection, and are we so well informed and prepared for a new seasonal outbreak?

It is no secret that the flu is caused by a virus that enters the body through the cells of the mucous membrane of the respiratory organs. The pathogen enters them, and then programs victims to create and release new viral copies, which leave the weakened mucosal cells and continue to infect new ones.

Thus, the virus cannot survive and reproduce unless it has found a host cell.

The virus invades a cell and makes copies of itself, which then infect new cells.

Illustration by Wikimedia Commons.

How it all began?

Influenza virus particles were first isolated in the laboratory at the very beginning of the twentieth century. The pathogen was called "chicken plague". In 1931, American scientists discovered this strain in pigs, and in 1933 - in humans.

Subsequently, it was called influenza type A. Later, scientists discovered type B. It is this couple that annually “incapacitates” millions of people across the planet.

By the way, another variety, the influenza C virus, causes only mild forms of illness, therefore it is harmless to humans and usually goes unnoticed.

What then do all these H1N1 or H5N1 designations that we hear and read about in the news mean? This is how experts have dubbed the numerous varieties of the variable influenza A virus, which allow specialists to identify a particular pathogen. Actually, this classification describes different subtypes of the main proteins - hemagglutinin (H) and neuraminidase (N) - located on the surface of the virus.

Schematic structure of the influenza virus. The hemagglutinin protein helps the virus enter the cell, and the neuraminidase enzyme helps it exit and continue to infect new cells.

Illustration by Centers for Disease Control.

Influenza is considered one of the “record holders for infectiousness.” It spreads rapidly through airborne droplets (and this is one of the fastest ways to transmit infection). The growing population of large cities and the developed system of modern transport greatly facilitate the path of the virus and contribute to massive outbreaks of the disease.

Therefore, one of the most serious and real threats is the uncontrolled spread of infection to cities and even entire countries (experts call such outbreaks epidemics and pandemics, respectively).

Pandemics of the last century

The world experienced several pandemics in the twentieth century. The largest outbreak in human history, the infamous “Spanish Flu,” began in 1918. The infection raged for 18 months and killed about 100 million people across the planet.

In 1958 and 1968, the world was swept by the “Asian” and “Hong Kong flu”. This virus affected about 15% of the population of Hong Kong, and in the United States the disease killed more than 30 thousand people.

The new century is also marked by a pandemic. In 2009, the World Health Organization announced a widespread outbreak of swine flu (the infamous H1N1). Then, according to various estimates, up to 250 million people in 140 regions of the world “caught” the infection.

The swine flu virus that caused the 2009 pandemic.

Illustration by Centers for Disease Control.

However, ordinary seasonal outbreaks of infection are also not nearly as harmless as they might seem. WHO experts report that the flu kills up to 650 thousand people worldwide every year!

Why do people get the flu in winter?

Typically, the flu “rules” during the cold season. First of all, this is due to the way the virus spreads. Experiments on animals confirm that airborne transmission of the pathogen occurs most easily at low temperatures and relative humidity.

In addition, in winter we spend more time indoors, lead a more crowded lifestyle and are more often in contact with more people. This also makes it easier for the virus to spread.

The cold, a developed transport network and being in public places make the task of the virus easier.

Photo by Global Look Press.

There is another reason. Studies have shown that during cold weather, the functioning of the immune system changes, and various inflammations occur more easily in a person, which also plays into the hands of the flu.

How to protect yourself and your loved ones from infection?

According to leading Russian experts, vaccination remains the most reliable protection against seasonal outbreaks of the virus. Its task is to prevent the uncontrolled spread of a dangerous infection.

The question may arise: but we have antiviral drugs, won’t they really stop the epidemic?

Let's explain with a simple example. Having caught the flu, a person does not feel any symptoms of the disease for the first two or three days, but at the same time he is already contagious. That is, by the time the first signs of the flu appear (and by the time you start taking antiviral medications), it will already have time to infect... from seven to twelve people, statistics say. So antiviral drugs are not able to save us from epidemics.

What is a vaccine and how does it actually work?

A vaccine is a drug that gives a person acquired immunity. Once in the body, this “test version of the disease” introduces the immune system to the infectious agent. In response, the body begins to produce antibodies. These substances represent a kind of police guidance for immune cells.

As a result, when encountering a real pathogen, they quickly recognize and neutralize the “intruder”, without waiting for any explanation from him as to who he is and what he is doing here, without allowing the disease to develop.

What types of vaccines are there?

Today, two types of vaccines are used to fight influenza. Live vaccines, as the name suggests, use live but weakened viruses. They are available in aerosol form and do not require injection.

Non-live, or inactivated, vaccines contain either small fragments of viruses (as a result, they are not able to infect humans), or only their antigens (the same hemagglutinin and neuraminidase). These vaccines are administered intramuscularly. They are safest for babies and pregnant women.

How are vaccines created?

The oldest and most proven method is growing vaccines in a fertilized chicken egg. The limited amount of this animal resource and the long process of obtaining the drug (six months or more) make the method not the most productive.

During the long “preparation”, the vaccine sometimes even manages to mutate, and the final strain in it no longer corresponds slightly to what was planned. In addition, “egg” vaccines are contraindicated for people with allergies to yolk proteins.

Another method is to obtain a vaccine in cell culture, which is faster and more efficient, and the required number of cells can be easily prepared for future use in case of a pandemic, when a lot of vaccine is needed.

Get vaccinated and get sick

It would seem, why, despite such extensive attention of specialists to the influenza virus and numerous developments to contain it, does the vaccine sometimes fail?

Doctors often hear the phrase: “I got vaccinated a couple of years ago, but now I’m still sick!”

This is due to the rapid variability of the influenza virus. The pathogen constantly mutates in response to human-invented vaccines.

For this reason, the antibodies produced by the body in response to the “outdated” version of the vaccine do not correspond to the new virus. Thus, even a year-old vaccination becomes ineffective during a new flu outbreak. This is why it is necessary to get vaccinated annually.

Do not forget that the effectiveness of vaccination is also affected by a person’s age and health status. In addition, the incoming virus does not always coincide 100% with the composition of the vaccine recommended in the new season, so people also sometimes get sick.

However, studies confirm that even in this case, the patient’s flu will pass in a much milder form and without critical complications.

It is also important to remember that the influenza vaccine does not protect against other acute respiratory viral infections that are easily confused with the flu. Therefore, for any suspicious symptoms, it is best to consult a doctor who will make an accurate diagnosis.

If the flu is so variable, then who knows what type to expect next year?

In order to keep influenza in check and prevent a repeat of the catastrophic events of 1918, a special WHO commission annually updates the composition of influenza vaccines.

Predictions about which strains will cause the next influenza outbreak are made by a “special department” with the complex name of the Global Influenza Surveillance and Response System (GISRS).

This is a huge network of 144 national influenza centers in 114 countries. Its staff continually collects and analyzes samples of influenza viruses collected around the world. The main task of experts is to identify the most common strains and new varieties of the pathogen. Based on the data obtained, vaccine compositions for the next season are being developed.

Typically, the drug includes three types of the most likely pathogen: two types A and one B (trivalent vaccines). There are also vaccines containing four strains of the virus: two types of virus A and B (they are called tetravalent).

Every year in February, a meeting is held where medical experts receive recommendations for the new season's flu vaccines.

And every year, doctors are faced with a lot of questions and doubts from their patients about vaccination. Some of them have already become myths of sorts. Let's figure out together how connected they are to reality.

The onset of influenza can be confused with another infection, but usually it is more severe and seriously affects a person’s health.

Photo by Global Look

Myths and legends

The best flu prevention is taking vitamins. Many people believe that they are safer, healthier and have no side effects.

Of course, you can strengthen your health with vitamins. Especially if there is a deficiency of valuable substances in the body (which, however, can only be determined with the help of appropriate tests). However, vitamins, of course, do not provide “specialized” protection against the flu, and any pills have side effects.

The flu shot weakens the immune system. Because of it, colds only catch more often.

In fact, it's the other way around. The vaccine activates our immunity. This is the principle of its operation. Let us emphasize once again that the flu vaccine only protects against the influenza virus and does not protect against other colds.

You can get the flu from the vaccine itself.

This is out of the question. Modern drugs used in Russia contain non-living influenza viruses or its fragments, which themselves do not cause the disease.

Let us clarify that mild illness, which sometimes bothers you two or three days after vaccination, is completely normal and does not mean that the person has caught the flu.

The body itself will cope with the disease.

People experience this infection in different ways. Someone recovers within a week, while others, under the same conditions, suffer serious complications (pneumonia, meningitis, heart damage) and even risk dying. So is it worth testing your own body for strength in this way?

Vaccines are dangerous and contain mercury.

Most vaccines (and not just influenza vaccines) contain thiomersal. This is an ethylmercury-based preservative that prevents bacteria and fungi from growing in vaccines. Ten years of observations have confirmed the safety of thiomersal for humans, WHO experts emphasize.

By the way, the opinion that “mercury” vaccines are not used in the USA and Europe is also erroneous. For example, during the 2010-2011 flu season, American specialists used more than 90 million doses of thiomersal vaccines.

Vaccinations cause autism in children.

Scientists have been researching the possible connection between autism and vaccination for many years ( Vesti.Nauka described in detail where the legs of this fairly common myth come from). However, there has been no conclusive evidence that any vaccines cause this disease.

Foreign vaccines are safe, but Russian ones can contain anything you want.

The production of any medicine must strictly comply with certain rules called Good Manufacturing Practice (the same GMP standard).

This is the “gold standard” that Russia, European countries and the United States adhere to. A vaccine with an “arbitrary” composition does not meet strict safety standards and simply will not reach the market.

Domestic and foreign vaccines are radically different from each other.

Experts emphasize that the antigenic composition of foreign and domestic vaccines is the same. Each of them necessarily contains particles of influenza viruses expected this season. Therefore, a person can choose any vaccine.

Nevertheless, there are still some differences. Thus, some Russian vaccines have a reduced concentration of viral antigens (five micrograms per dose instead of the WHO recommended fifteen). Moreover, this drug contains “enhancer” substances (adjuvants) that boost the immune system, so it is not inferior to other drugs.

True, this information does not yet have clear confirmation (except for the statements of the vaccine manufacturers themselves), family doctor Galina Aleksandrovna Kuzmenkova told a Vesti.Nauka correspondent.

In addition, in our country, trivalent vaccines are most often used, while drugs with four types of viral antigens are already quite widespread abroad.

Who needs to be “fully armed”?

Flu vaccinations should be given to everyone who is in the so-called risk group. These are people over 65 years of age, pregnant women and those who suffer from chronic diseases (such as diabetes, hypertension). This also includes small children from six months to five years, service workers and doctors.

Let us add that to prevent a flu epidemic in Russia, it is necessary that 45% of the population (and 75% of people at risk) be vaccinated against influenza.

How to protect yourself from the flu if vaccination is contraindicated? And how can you reduce your risk of getting sick in general?

Let us recall some “rules of good manners” during outbreaks of infection. They will reduce the likelihood of getting the flu.

Remember to wash your hands regularly, especially if you have been in public places. Although the virus is transmitted through the air, it can settle on a variety of objects (handrails in transport, ATM keyboards and even money), which means it enters the body with dirty hands.

By the way, during the epidemic season, touch your eyes, nose and mouth with your hands as little as possible. As we have already said, the virus enters the body through the mucous membranes.

It is better to cough and sneeze into your elbow, tightly covering your mouth and nose. If you are already contagious, this will reduce the risk to the people around you.

Also, obviously, you should visit crowded places less often and avoid close contact with people who have a cold.

When you sneeze and cough droplets of saliva, a huge amount of virus is released. Protect those around you - use a special mask or sneeze into your elbow.

Photo by Global Look Press.

If you feel unwell, stay home and call a doctor. It's time to be an introvert! Limit communication with family members as much as possible, wear a special protective mask (it needs to be changed every two to three hours) and ventilate the room often.

Do antiviral medications help?

WHO recommends the use of some modern antiviral drugs if influenza does develop. They shorten the time of illness and eliminate many complications.

However, viruses (just like bacteria), “getting acquainted” with the drugs available in the human arsenal, develop resistance to them. Therefore, today no one is immune from a situation where such a drug does not work.

What does the future hold for us?

To rid humanity of the burden of influenza, experts are working in two key areas.

Firstly, it is important for them to predict as accurately as possible the strain of the pathogen that will be active in the coming season. To do this, experts create various models that predict the genetic evolution of the influenza virus.

Secondly, virologists around the world are developing promising, quick-to-produce vaccines. They will make it possible to select the expected strains of the new season much closer to the beginning of the influenza outbreak. This means that the virus will have less time to mutate and outwit the newly created vaccine.

To date, drugs made from artificial virus-like particles that imitate the protein structure of the virus are already being tested.

Vaccines based on a small artificial DNA (plasmid) into which the genetic material of the virus is inserted are also showing promising results in preclinical trials.

Viral vector technology also deserves attention. This intricate name was given to viruses that are not dangerous to humans, which scientists have adapted as a “carrier” of influenza proteins. This strategy will protect people from many strains of the pathogen at once and will simplify the composition of the vaccine.

Researchers also place great hopes on the so-called “universal” vaccines ( Vesti.Nauka constantly monitors such developments). Such drugs are also designed to cope with several strains of the influenza virus at once, maintaining effectiveness for several years and eliminating the need for annual “vaccination”.

Is it possible to eradicate the flu?

Vaccines save many lives every day. Thanks to them, humanity got rid of smallpox and almost defeated polio. Will the flu also be a thing of the past?

To answer this question, recall that the influenza A virus is widespread among poultry and pigs (in whose bodies it mutates and sooner or later “learns” to infect humans). Therefore, it is unlikely that it will be possible to completely get rid of it. However, the new generation of vaccines will eliminate cases of discrepancies between the recommended strains and the “hero of the season” virus and will make it possible not to be vaccinated every year.

In other words, people will get sick from influenza type A less often and more easily, and massive outbreaks will probably be completely avoided.

There is one more good news. Type B viruses do not infect animals, but “take root” only in the human body. This means that new generation vaccinations and mass vaccination can (at least theoretically) eradicate this virus, scientists say.

Be attentive to your health and do not neglect the benefits of medicine. Any prevention is better than cure. Any modern treatment is better than “grandmother’s recipes”, disproven by science.

Source: Vesti.Nauka

Varieties of influenza

A person can get swine or chicken flu during an epidemic of this disease. There is a distinction between seasonal flu and regular flu, which can be caught all year round simply on the street, without direct contact with a sick person.

Seasonal influenza outbreaks occur from October to March. Young people and children are most often affected by the disease (see video). It is important to know how long the incubation period for the flu is to accurately identify the problem.

On the one hand, older people have chronic diseases, which makes them more vulnerable to the virus. But they are not as often on the street as young people, visit public places less often and do not have daily contact with colleagues, classmates or classmates - and these are possible sources of transmission of the virus.

Young people have a stronger immune system, and the body more actively resists viruses. But the risk of catching them is much higher.

How often you can get vaccinated and how to prepare for it so as not to get swine, chicken or regular flu is shown in the video.

Flu treatment at the Mama Papa Ya clinic

For those suffering from the flu, the network of family clinics “Mama Papa Ya” offers various medical services at an affordable price:

treatment of family members of any age;
if necessary, consultation with an ENT doctor and other specialists;
flu vaccination.

The clinic has a network of branches in Moscow and other cities. You can make an appointment or call a doctor by phone or on our website.

Reviews

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I would like to express my gratitude to the staff of the clinic: Mom, Dad, and me. The clinic has a very friendly atmosphere, a very friendly and cheerful team and highly qualified specialists. Thank you very much! I wish your clinic prosperity.

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How effective is vaccination?

Influenza vaccines are a key preventative measure that have been used for over sixty years. Efficacy can be assessed based on the likelihood of infection with the virus and the occurrence of complications and side effects. After mass vaccination, the following results are noted:

Reduction in mortality in elderly people – 55-68%.
The need for inpatient treatment for patients over 50 years of age is 48%.
The probability of contracting ARVI and influenza among the elderly is up to 90%.
Infection with the influenza virus in children after vaccination ranges from 60 to 92%.
The occurrence of otitis media as a complication of influenza in schoolchildren – 30-35%

But, despite its fairly high effectiveness, flu vaccination has side effects. They are not observed so often, but you still need to be prepared for the following temporary symptoms:

Pain in joints and muscles;
Headache;
Temperature rises to 37.5 degrees;
Redness of the skin and swelling at the injection site.

All these symptoms usually disappear within 1-2 days. Serious complications and side effects after influenza vaccination can be observed in only one person out of a million vaccinated people. Therefore, all fears and concerns about the flu vaccine are groundless - the video talks about this.

There are certain precautions that can be taken to avoid complications during vaccination. First of all, the doctor needs to inform about all chronic diseases in the medical history, infectious diseases suffered in the last month, and about taking any medications.

You must notify your doctor of any allergies to medications or food. Almost all vaccines are made from chicken egg white. Therefore, if a patient has an individual intolerance to this product, flu vaccination is contraindicated for him - it can cause a severe allergy.

Other contraindications to vaccination are:

Any infectious or chronic diseases in the acute stage;
Allergy to vaccines for other diseases;
Increased body temperature and acute pain;
Children up to six months of age;
First trimester of pregnancy.

Getting a flu vaccine is an effective way to reduce your risk of contracting the virus, and if you do become infected, the vaccine reduces hospitalizations and deaths from the disease (see detailed video).

Morphology and structural proteins

What is a viral particle made of and what do the letters “H” and “N” mean? The name of a particular form of influenza is not a random combination of symbols: it indicates exactly which types of proteins of the two types are present on the surface of the virus. They determine the ability of a given strain to infect certain organisms, which is associated with the likelihood of “recognition” of the virus by the immune system (these structural features are used in the development of various drugs).

Viruses of the Orthomyxoviridae family have a lipid envelope formed from part of the host cell membrane (19 and 20). Surface proteins are included in the membrane. Influenza viruses have two of them - hemagglutinin (H), which is necessary to bind to cellular receptors and penetrate the host cell, and neuraminidase (N), which cuts off the newly formed virus particle from cellular receptors and allows it to move to a new cell. The virus membrane also contains channels formed by the M2 protein - they serve to unpack the particle in the cytoplasm. Under the virus membrane there is a matrix layer formed by the structural protein M1. In the center of the particle there is genetic material, represented by eight RNA molecules, each of which is connected to NP (nucleoprotein) structural proteins and the polymerase complex responsible for their copying (5, 21, 22).

Influenza viruses can be either spherical or filamentous (23). The diameter of the spherical particles is comparable to the diameter of HIV - 80-120 nm. Variations in the form of different types and strains are due to differences in the structure of the matrix proteins, which are located directly below the membrane (24 and 25). Individual influenza virus proteins are being studied as possible targets for antiviral drugs. Thus, much attention is paid to the development of neuraminidase inhibitors that block the work of this enzyme, which prevents the new virus from leaving the cell (26). The drugs Tamiflu and Relenza, in particular, work on this principle (27). Drugs have also been developed that prevent the particle from unpacking in the cytoplasm of an infected cell or that contain antibodies to various types of hemagglutinin (28).

The key protein molecules that ensure the vital activity and reproduction of the influenza virus are the surface protein hemagglutinin, the neuraminidase enzyme and the M1 matrix proteins. Based on its structural principle, hemagglutinin resembles the surface protein of the Ebola virus (29 and 30). This protein is a homotrimer with transmembrane and surface parts, which are linked by disulfide bonds. Virus entry into the cell occurs after hemagglutinin binds to cellular receptors bearing sialic acid (31). The virus enters the cytoplasm as part of a vesicle. When the environment inside the vesicle becomes more acidic, hemagglutinins change their conformation and cause fusion of the viral membrane and the vesicle membrane (32). M2 proteins form channels through which hydrogen ions enter the viral particle, disrupting the interaction between the matrix and the genetic material of the virus and thereby allowing the latter to enter the cytoplasm (33). The drugs Remantadine and Amantadine (as well as their analogues) are aimed at inhibiting the M2 protein and preventing virus unpacking; however, they are less effective than neuraminidase inhibitors and are now rarely recommended for the treatment of influenza (27).

The work of neuraminidase is important during the final stages of the virus life cycle. This protein consists of four identical subunits (34), and its function is to cleave terminal sialic (neuraminic) acid residues from glycosylated receptors to which hemagglutinin binds. Without this, newly formed viral particles will not be able to detach from the surface of the host cell (35). The cleavage of sialic acid also prevents the cell from being re-infected by other viral particles. Neuraminidase inhibitors, which slow down the spread of the virus in the body, are the active components of the anti-influenza drugs Zanamivir and Oseltamivir (36). However, oseltamivir (the active ingredient in Tamiflu) stops working if the 274th amino acid histidine in the virus neuraminidase changes to tyrosine. Zanamivir (the active ingredient of Relenza) does not lose activity in this case, but it provokes side effects, so it is recommended to be used only in cases where Tamiflu does not work (27 and 37).

M1 matrix proteins play a key role in the assembly of new viral particles (38 and 39). Before the formation of new virions, they accumulate on the inner side of the cell membrane, interacting with both surface proteins and the viral genome complexes located in the cytoplasm, due to which all the components of the future virus come together. The presence of a matrix is characteristic of viruses with a lipid membrane, such as HIV or Ebola virus (40 and 41). In addition, these viruses are characterized by budding from specific areas of the cell membrane - lipid rafts, the molecular composition of which makes them somewhat less labile compared to other areas of the membrane (42).

Transmission mechanism

The mechanism of transmission of the disease is airborne. The virus is transmitted through direct contact with a sick person, through sneezing, coughing, kissing, or shaking hands. ARVI and flu can be easily caught on the street. Other sources of infection are handrails in public transport, banknotes, and trolleys in a supermarket.

If a person sneezes or coughs, splashes of saliva scatter within a radius of two meters. The influenza virus enters the human body, penetrates the nasopharyngeal mucosa and begins to multiply. Cells affected by the virus die and toxins are released into the body.

At the same time, a person feels headaches, muscle aches, his body temperature rises, and a runny nose and cough begin. The patient's sleep is disturbed, he becomes irritable, and quickly gets tired. It is important not to contact the patient in the first three days after the onset of the disease - during this period it is most dangerous. In children it lasts up to seven days.

Outside the human body, the human virus remains viable for 2 to 8 hours, provided that the surfaces on which it settles are not disinfected. At temperatures of 100 degrees Celsius and above, the virus dies instantly.

Therefore, it is very important to wash the patient’s things in very hot water and treat all surfaces and objects with antiseptic solutions. This is nonspecific prevention of influenza, as the video in this article will tell you about.

Inside the virus: how the genetic material is packaged

The main goal of any virus is to reproduce its own genome by creating copies. Information about all the structural and functional components of the virus is contained in RNA. Each virus particle contains one copy of the genome, compactly arranged in eight separate helical structures. The total length of these ribonucleic acid molecules exceeds the diameter of the virus by N times. An important role in the transfer and storage of genetic information is played by the fact that RNA is contained in the virus as part of ribonucleic complexes.

The genetic material of influenza is divided into parts, each of which is responsible for the synthesis of individual viral proteins. Therefore, if different strains enter the same cell during the assembly of new particles, hybrid strains can be formed, which accelerates the evolution of viruses and complicates the fight against them (43). The influenza RNA segments are not equal, and a fixed set of eight different RNAs must end up in the particle, each of which performs its own function. How this is achieved in nature is not entirely clear. Apparently, there is a specific interaction between viral ribonucleoprotein complexes (RNPs) that ensures the assembly of different parts of the genome in the required composition (44).

Publications of research results describing the structure of viral RNPs began to appear relatively recently. One of the latest and most detailed works on this topic was prepared and published in the journal Science (45) by teams from the laboratories of Jaime Martin-Benito and Juan Ortin. Dr. Martin-Benito comments on the specifics of their research:

When we began to study the structure of the complete RNP of native influenza viruses at the National Center of Biotechnology in Madrid, all available information on this topic was limited to X-ray crystallographic analysis of the nucleoprotein without RNA (46 and 47) and polymerase fragments (48 and 49). RNPs are variable in size, flexible, and supercoiled structures (50), making research very difficult. In this situation, cryoelectron microscopy turns out to be a unique method capable of producing an acceptable result. The main problems were caused by differences in the length of individual RNPs, as well as their mobility. To overcome this, we separately analyzed the central and terminal parts of RNPs isolated from isolated virions and then performed their 3D reconstruction (45). The most difficult step here was the classification of the resulting images. It was necessary to obtain homogeneous groups, which would allow for the final reconstruction. More than 90 thousand images were used to generate the final structure. We spent millions of hours of computer time on this."
Jaime Martin-Benito (Spanish National Center for Biotechnology, Madrid, Spain)

The structure and conformation of RNPs, as well as their interaction with other viral proteins, provide them with specific properties and functions. The influenza genome is represented by eight RNA molecules of negative polarity and different lengths. This number of genome segments is typical for all orthomyxoviruses (except for togotoviruses, which contain six RNA molecules). RNA binds to polymerase complexes (48) and NP protein (51) to form RNP (44). RNPs are organized into double helices of two strands of RNA associated with NP proteins and positioned opposite each other (45).

The difference in length of different influenza RNPs is due to differences in the lengths of their RNA segments. The three longest segments are about 2500 nucleotides in length, while the shortest segment is only slightly longer than 800 nucleotides. RNPs are usually grouped in a particle around one of the longest RNPs in such a way that the polymerase ends of all RNPs are collected together, interacting with matrix proteins at one of the poles of the virion. NEP proteins also fall into this region, whose function is to export newly synthesized RNPs from the cell nucleus to the site of virus assembly.

One of the problems currently arousing active interest in the community of structural virologists is the study of the reasons for the specific packaging of the required set of different RNPs in each new particle. It is believed that the RNA molecules within each RNP are capable of specifically interacting with the RNA of neighboring segments. We reflected this point in our model, but the specific mechanisms of this interaction are the subject of further research (44, 45, 52).

Many membrane viruses are characterized by the presence in virions of proteins captured from the host cell. Thus, actin and cyclophilin are found inside HIV, and the membrane of this virus contains proteins related to the major histocompatibility complex, which makes the virus less vulnerable to the immune system (53, 54, 55). The presence of human proteins in the influenza virus particle has not yet been reliably demonstrated, although some data on this issue have been published (56).