Types of computer viruses and how they are dangerous. What are computer viruses, their types Different types of viruses

Good day! Each of us has heard such a word as a computer virus. Some people know quite a lot about this concept, but for most readers, this word remains mysterious, incomprehensible, something distant.

What does a computer virus mean? Let's first define a common virus. A virus is a kind of crystal that has its own DNA, cytoplasm and other elements. But the virus does not have its own nucleus, is not an independent organism and cannot exist outside any living being, be it a cell or a multicellular organism.

Viruses can be in hibernation, incubation, or active periods. All this also applies to computer viruses. Their essence is really similar. They also integrate into another organism, i.e. program, change its code, actively multiply, sometimes even damage the PC hardware. Just like common viruses, the types of computer viruses are quite diverse.

We can say that a computer virus is a program that is capable of creating multiple duplicates, being embedded in the code of other software, in the system's memory, and introducing its numerous duplicates in various ways.

The task of computer viruses is to malfunction of various software systems, delete many files, malfunction in the structure of information, block the operation of various PC nodes in order to impede their performance.

And this is really so, just three days ago, my nephew came to see me, I downloaded games for him via torrent. In the process of downloading, various shortcuts of various programs that I did not need began to appear on the monitor screen.

Then I had to delete these softwares, but this is nonsense, the main thing is that a virus that I ate removed was introduced into it. And then he did it in the "Safe PC mode" (In this mode, only a part of the drivers and other programs are turned on, the most necessary ones, which makes it possible to search for a virus without interruptions in the work of the antivirus).

I advise you to use it, because Many viruses try to disable the antivirus first, which is what happened to my computer. It turns on quite easily, you click on the hard reset button (next to the "Start" button), during the boot process you will be offered three options for turning on, one of which is "Normal mode" and "Safe".

I also want to give you advice, when you download through, always watch what you download, how many files. Usually there should be one file if it is one program, not several. If there are several of them, this is already suspicious!

Also watch out for so-called files with the name "Silent installation" among the downloaded applications. If you see such a file, uncheck it right away. Otherwise, it is not clear what you will install!

And one more piece of advice, if you use Kaspersky, it is better to choose KIS. it blocks similar silent install files! In general, it is not worth saving on a good antivirus! But back to the types of viruses.

Types of computer viruses and their stages

Regarding the stages of occurrence of the virus, it happens Latent, Incubation and Active (The most dangerous!).

A) Latency period- in this period, the virus is in the OS without active actions. A person may not even notice it. He is able to notice in this state only, and then when the entire computer begins to scan.

V) Incubation period- unlike the previous one, it is a rather dangerous period. During this period, the virus software code activates and duplicates itself in many ways, distributing its duplicates not only to various parts of a particular PC, but also to the worldwide network.

Read about symptoms that signal the presence of a virus on the computer... How a computer, antivirus program or browser reacts to viruses. Malware or viruses can plunge your computer into chaos. They can deactivate antivirus software and leave your computer vulnerable to other malware. software, interfere with the normal functioning of the computer, or damage the operating system files.

Ransomware viruses encrypt user data in such a way that it is almost impossible to decrypt or recover it. Viruses can access any data, be it personal files, bank data or user passwords, and create duplicate accounts.

What can you do to protect yourself and your computer from viruses? You need to start by installing an anti-virus program. It also doesn’t hurt to learn the skills to use your PC safely. A common reason for the infection of a computer with viruses or other malware is the lack of computer literacy of the user, which is also worth tightening up.

New types of viruses and malware appear all the time, so they cannot always be detected by every anti-virus program, at least until they are entered into the virus signature database. Such fresh viruses can enter the system and go through all the software protections.

If you accidentally downloaded a suspicious file that contains a virus or clicked on an email attachment, your system may be infected with viruses such as: Trojan, Rootkit, Worm, Backdoor, Junkware or Malware... Therefore, before clicking on an unknown file or link, it is better to think twice and make sure that the antivirus program installed on your computer has the latest antivirus signatures.

So how do you tell if your computer is infected with viruses? Here are some clear signs that signal viruses or other malware on your computer:

And now in detail:

These are just the most common ways to identify viruses, malware or ransomware on your computer and their symptoms. And how quickly the user can deal with such programs on his PC depends on the safety of his data and files.

Acellular infectious agent. It has a genome (DNA or RNA), but lacks its own synthesizing apparatus. It is capable of reproducing only when it gets into the cells of more highly organized creatures. Reproducing, it damages the cells in which this process takes place.

Each of us is faced with viruses many times in our lives. After all, it is they that cause most of the cases of seasonal colds. The body successfully copes with the usual ARVI itself - our immunity can withstand the attacks of infections. But not all viral diseases are so harmless. On the contrary, some of them can lead to serious damage to tissues and systems, cause severe chronic diseases, become the cause of disability and even death. How to understand the variety of viruses? How to protect yourself from the most dangerous? And what if the disease has already been detected? What are antibodies to the virus and which ones appear during the disease?

Human viruses

To date, more than 5 thousand different viruses have been described, but it is assumed that there are millions of their species. They are found in all ecosystems and are considered the most abundant biological form. Moreover, these infectious agents are capable of infecting animals and plants, bacteria and even archaea. Human viruses occupy a special place, because they cause the greatest number of diseases. Moreover, the diseases are very diverse in terms of their severity, prognosis and course.

At the same time, it is with viruses that an important condition of evolution is associated - horizontal gene transfer, in which genetic material is transmitted not to descendants, but to other types of organisms. In fact, the virus has contributed in no small measure to genetic diversity. For example, studies have shown that the human genome is 6-7% composed of various virus-like elements and their particles.

Virus in men

Human viruses are capable of equally infecting the organisms of children and adults, as well as representatives of both sexes. However, there are species that pose a particular danger to a certain category of the population. An example of a dangerous virus in men is the paramyxovirus, which causes mumps. Most often, the mumps passes without any particular complications, with a noticeable lesion of the salivary and parotid glands. However, the virus in men poses a great danger, since more often than in women, it also affects the sex glands, and is capable of causing orchitis in 68% of cases, an inflammation of the testicles. And this, in turn, can cause infertility. This complication is typical for adults and adolescents; in boys under 6 years of age, orchitis occurs only in 2% of cases. Also, the virus in men can provoke the development of prostatitis.

Paramyxovirus is highly contagious, transmitted by airborne droplets, including during the incubation period, when there are no symptoms of the disease yet. There is no specific treatment for mumps, so best protection from disease - vaccination. Mumps vaccination is included in the mandatory routine vaccination calendar in many countries.

Virus in women

Now special attention is focused on the human papillomavirus in women, because some types of it have been proven to be associated with the development of cervical cancer. In total, according to the World Health Organization, there are at least 13 such types, but the greatest danger is represented by the 16 and 18 types, which are characterized by the highest oncological risk. It is with these two viruses in the body that 70% of all cases of cervical cancer and precancerous conditions are associated.

At the same time, with timely diagnosis and removal of papillomas, such an outcome can be avoided. Cancer, as a complication of HPV, with normal immunity develops within 15-20 years, therefore, systematic examinations by a gynecologist will help in time to identify a dangerous virus in women of different ages. It should be said that a factor such as smoking affects the activity of the papilloma virus - it contributes to the degeneration of genital warts into a malignant neoplasm. Since there is no specific treatment for HPV, the World Health Organization recommends vaccination against types 16 and 18.

Viruses in women are especially dangerous during pregnancy, since, due to their small size, they easily penetrate the placental barrier. In this case, the severity of the course of the disease in the mother and the likelihood of fetal damage are not related. It often happens that latent or easily transferred viral infections cause serious pathologies in the fetus, can cause miscarriage.

It should be said that most viruses are dangerous only if a woman becomes infected with them during pregnancy. In this case, the mother's body does not have time to develop enough antibodies to protect the fetus, and the virus causes serious damage.

The most dangerous is early pregnancy, up to 12 weeks, since it is now that embryonic tissues are being formed, which are most easily affected by viruses. In the future, the risk of complications decreases.

Viruses transmitted through blood and its components, as well as other biological fluids, are also dangerous during childbirth. Because the baby can become infected with them, passing through the birth canal.

The most dangerous viruses in women during pregnancy:

• Rubella virus.

In the first trimester of pregnancy, the likelihood of fetal damage is 80%. After 16 weeks, the risk of injury is significantly reduced, and most often pathologies are manifested only by deafness. In the early stages, the virus can cause bone damage, deformity, blindness, heart defects, and brain damage in the fetus.

• Herpes virus 1 (HSV-1) and 2 (HSV-2) types.

The most dangerous is the second, genital type, with which a child can become infected during the passage of the birth canal. In this case, the development of severe neurological damage, among which the most dangerous is encephalitis. In some cases, herpes simplex virus type 2 can kill a child. HSV-1 is asymptomatic, most often easily tolerated by the fetus and does not cause significant harm to health.

Infection of the mother at an early stage can lead to the development of fetal pathologies incompatible with life, as a result of which a miscarriage will occur. In addition, the disease is dangerous not only by the effect of the virus itself, but also by the general intoxication of the body. It, in turn, can cause fetal hypoxia, developmental delay, and more. That is why WHO recommends that pregnant women get vaccinated against influenza, especially during an epidemically dangerous period.

Botkin's disease (hepatitis A) is very often carried over in childhood, so it is quite rare during pregnancy. However, if the infection did occur, the disease will be severe. Hepatitis B and C can pose a threat to an unborn child, especially if a woman contracted them during pregnancy. Chronic hepatitis B and C are dangerous during childbirth. Most often, it is the hepatitis B virus that is transmitted in this way. Moreover, in congenital form, it is much more difficult to treat and in 90% of cases becomes a chronic incurable form. Therefore, women planning a pregnancy may be advised to vaccinate against hepatitis B. If there is a chronic infection, then it is worth having a caesarean section. The hepatitis E virus rarely poses a serious danger, but it is during pregnancy that it can lead to serious consequences for the fetus and the woman herself. Including cause death from kidney failure.

Most often, infection occurs in childhood, after which a person is a carrier of the virus, while no symptoms appear. Therefore, as a rule, by the time of pregnancy, this virus in women does not pose a particular danger. In the event that infection with cytomegalovirus occurred during the gestation of a child, the fetus in 7% of cases can get complications in the form of cerebral palsy, hearing loss, etc.

The human body develops specific immunity to various viruses that it encounters throughout life. This explains the fact that a child suffers from ARVI (acute respiratory viral infections) more often than an adult. The frequency of infection with the virus is the same at different ages, but in an adult, the immune system suppresses the infectious agent even before symptoms appear. In domestic pediatrics, there is the concept of "frequently ill child", that is, one who carries more than 5 ARVI per year. However, foreign doctors believe that 6 infections per year are the norm for children under 3 years old. And a child attending kindergarten can carry up to 10 colds annually. If acute respiratory viral infections pass without complications, they should not cause concern, ”says well-known pediatrician Yevgeny Komarovsky.

Also, childhood is characterized by a number of certain viral infections that are extremely rare in adults. Among them:

• Chicken pox.
• Measles.
• Rubella.
• Mumps.

It should be noted that children of the first year of life are practically not susceptible to these diseases, since even in the womb they receive antibodies to viruses from the mother's blood through the placenta.

Despite the fact that these infections are most often easily tolerated by children, there is still a risk of complications. For example, measles often leads to pneumonia and is one of the leading causes of infant mortality, while mumps causes inflammation in the genitals. Therefore, there are effective vaccinations against all of the above viral infections - timely immunization makes it possible to obtain immunity without a previous illness.

Virus as a form of life

Also, these non-cellular infectious agents, this is how viruses are now characterized, lack basic and energy metabolism. They cannot synthesize protein, as other living organisms do, and outside the cell they behave like a particle of a biopolymer, not a microorganism. The virus outside the cell is called the virion. It is a structurally complete viral particle that is capable of infecting the host cell. When infected, the virion is activated, forms a "virus-cell" complex and it is in this state that it is able to multiply, while transmitting its genetic code to new virions.

Viruses, like other living organisms, can evolve by natural selection. It is due to this that some of them, for example the influenza virus, are capable of constantly causing epidemics, since the developed immunity against new forms does not work.

The virion size is 20-300 nm. Thus, viruses are the smallest infectious agents. For comparison, bacteria are on average 0.5-5 microns in size.

As already mentioned, the virus differs in that it can multiply and is active only inside a living cell. Most types of viruses completely penetrate the cell, but there are those that introduce only their genome into it.

The life cycle of this extracellular agent can be divided into several stages:

• Attachment.

Moreover, it is at this stage that the circle of hosts of the virus is determined, because often these are highly specialized microorganisms that are able to interact only with certain types of cells. Thus, viruses that cause respiratory diseases prefer cells of the mucous membranes of the respiratory tract, and HIV is able to interact only with a specific type of human leukocytes.

• Penetration.

At this stage, the virus delivers its genetic material into the cell, which will later be used to create new virions. Viruses are able to multiply in different parts of the cell, some use the cytoplasm for these purposes, others use the nucleus.

• Replication is the reproduction of copies of the genetic material of a virus.

This process is only possible inside the cell.

• The release of virions from the host cell.

In this case, the membrane and the cell wall are damaged, and the cell itself dies. However, in some cases, viruses remain in the cell without damaging it and multiplying with it. Infected cells can exist for a long time, and the disease itself does not make itself felt, turning into a chronic form. This behavior is typical, for example, of the herpes virus, papillomavirus and others.

Virus genome: DNA-containing and RNA-containing

Depending on the form in which the genetic material of viruses is contained, it is customary to divide them into DNA-containing and RNA-containing (Baltimore classification).

• DNA viruses.

Their replication (reproduction) occurs in the cell nucleus, and the process of forming new virions in most cases is completely provided by the synthetic apparatus of the cell.

• RNA viruses.

A large group that mainly multiplies in the cytoplasm of the cell. Among the RNA-containing agents, it should be said separately about retroviruses, which differ from others in that they are able to integrate into the DNA of the host cell. These viruses are often distinguished into a separate group for their unique property of reverse transcription. In normal genome replication, information is transferred from DNA to RNA, and retroviruses are able to make double-stranded DNA based on single-stranded RNA.

Depending on how active the virus is and how destructive the genetic material is for the cell, its effect on it also depends. For example, one of the most dangerous infections, HIV, is referred to as retroviruses. On the other hand, it is precisely this kind of integration into the genome of a living cell that allowed some types of this type of virus to gain a foothold in DNA - scientists associate with them the species diversity of living organisms, as well as evolutionary processes.

Types of viruses

Viruses, despite their small size and dependence on the cell, still know how to protect the genetic material they carry. It is for this, first of all, that the shells of the virus are responsible. Therefore, viruses are sometimes classified according to their types.

Compared to other infectious agents, the structure of viruses is quite simple:

• Nucleic acid (RNA or DNA).
• Protein coat (capsid).
• Sheath (supercapsid). Not found in all types of viruses.

Virus capsid

The outer shell is made up of proteins and serves as a protective function of the genetic material. It is the capsid that determines which types of cells the virion can attach to; the membrane is also responsible for the initial stages of cell infection - membrane rupture and penetration.

The structural unit of the capsid is the capsomere. While in a cell, the virus, by self-assembly, reproduces not only genetic material, but also a suitable protein coat.

In total, 4 types of capsids are distinguished, which are easy to distinguish by their shape:

• Spiral - capsomeres of the same type surround single-stranded DNA or RNA of the virus along their entire length.
• Icosahedral - capsids with icosahedral symmetry, which sometimes resemble balls. This is the most common type of virus that is capable of infecting animal cells, and therefore infecting humans.
• Oblong - one of the subspecies of the icosahedral capsid, but in this version it is slightly elongated along the line of symmetry.
• Complex - includes spiral and icosahedral types. Rare.

Virus envelope

For additional protection, some types of viruses surround themselves with another envelope formed from the cell membrane. And if the capsid is formed inside the cell, then the supercapsid "captures" the virus, leaving the cell.

The presence of a shell, consisting essentially of a material related to the body, makes the virus less visible to the human immune system. This means that such vibrios are highly infectious, they are able to stay in the body longer than others like them. Examples of enveloped virions are HIV and influenza virus.

Virus infection

Signs of the presence of a virus in the body are highly dependent on the type of virus. Some infections cause an acute course of the disease, pronounced characteristic symptoms. These include the influenza virus, measles, rubella. Others, on the contrary, may not appear for many years, while harming the body. This is how the hepatitis C virus, HIV and other dangerous infections behave. Sometimes their presence can only be detected by specific blood tests.

Virus Infection Methods

Since viruses are widespread and capable of infecting various cells of the human body, they have access to all the main routes of infection transmission:

• Aerogenic (airborne) - viruses are carried through the air, by coughing, sneezing or even simple conversation.

This route of transmission is typical for all acute respiratory viral infections, including influenza, as well as measles, rubella and other infections.

• Alimentary (fecal-oral) is a transmission route characteristic of the types of viruses that can accumulate in the intestines, excreted with feces, urine, vomit.

Infection occurs through dirty water, poorly washed food, or dirty hands. Examples are hepatitis A and E, poliomyelitis. Often, such infections are seasonal in nature - infection with the virus occurs in warm weather, in summer.

• Hematogenous (through blood and components) - the infection enters through wounds, microcracks in the skin.

Viruses transmitted in this way are dangerous during blood transfusion, surgery and other medical procedures, injection drug addiction, tattooing and even cosmetic procedures. Often, the infection is able to penetrate through other biological fluids - saliva, mucus, and so on. The viruses of hepatitis B, C and D, HIV, rabies and others are transmitted through the blood.

• Transmissible - transmitted by insect and tick bites.

Among the most common diseases caused by these viruses are encephalitis and mosquito fever.

• Vertical - the virus is transmitted from mother to child during pregnancy or childbirth.

Most diseases with hematogenous transmission can be transmitted in this way. In the first trimester of pregnancy, rubella, influenza and other diseases are dangerous.

• Sexual - infection occurs through unprotected sexual intercourse.

The route of transmission is also characteristic of viruses transmitted through blood and components. According to WHO, four viral infections are most often transmitted in this way - HIV, herpes, papilloma virus, hepatitis B.

Not all viruses that enter the human body are capable of causing illness. Any foreign organism that comes to us immediately meets the cells of the immune system. And if a person has developed acquired immunity, then the antigens will be destroyed even before the symptoms of the disease develop. Our immune system provides stable protection, often for life, against many viruses - acquired immunity is developed after contact with a virus (illness, vaccination).

Some infections, such as measles, rubella, polio, can cause epidemics among children and practically do not affect the adult population. This is precisely due to the presence of acquired immunity. Moreover, if vaccination provides "collective immunity", such viruses will not be able to cause epidemics in children's groups.

Some species, such as the flu virus, can mutate. That is, every season a new strain of the virus appears, for which the population has not developed immunity. Therefore, it is this infection that can cause annual epidemics and even pandemics - infection of the population of several countries or regions.

Among the most famous pandemics that humanity has experienced, different strains of influenza are quite common. These are, first of all, the "Spanish flu" of 1918-1919, which claimed 40-50 million lives, and the Asian flu of 1957-1958, during which about 70 thousand people died.

Smallpox viruses also caused pandemics, which in the twentieth century alone caused 300-500 million deaths. Thanks to mass vaccinations and revaccinations, this virus was defeated - the last case of infection was recorded in 1977.

The human immunodeficiency virus (HIV), which is also considered a pandemic disease in terms of prevalence, raises serious concerns.

Symptoms of the penetration of the virus into the body

Different viruses in the body behave differently, manifest themselves with their own symptoms, and sometimes the disease is asymptomatic, without making itself felt for a long time. For example, hepatitis C most often does not manifest itself by external signs, and the disease is detected only at an advanced stage or by accident - according to blood tests. Influenza, on the contrary, is always acute, with an increase in temperature, general intoxication of the body. Measles and rubella are characterized by a specific skin rash.

There are viruses that are successfully suppressed by the immune system, but remain in the body. A classic example is herpes simplex, infection with which is life-long and incurable. However, the disease rarely causes serious inconvenience, manifesting itself only occasionally as ulcers on the lips, genitals and mucous membranes.

Many types of human papillomavirus occur with subtle symptoms, the infection does not require treatment and goes away on its own. However, there are HPVs that form that can degenerate into malignant neoplasms. Therefore, the appearance of any type of papilloma or condyloma is a reason to pass an analysis for viruses, which will help determine the type of infection.

Signs of a viral infection

Most often, we are faced with viruses that cause acute respiratory infections. And here it is important to be able to distinguish them from diseases caused by bacteria, since the treatment in this case will be very different. SARS provoke more than 200 types of viruses, including rhinovirus, adenovirus, parainfluenza and others. However, despite this, infection with the virus still manifests itself with similar symptoms. ARVI is characterized by:

• Low subfebrile temperature (up to 37.5 ° C).
• Rhinitis and cough with clear mucus.
• Headaches, general weakness, poor appetite are possible.

The flu, which always begins acutely, within several hours, is characterized by high fever, as well as general intoxication of the body - severe malaise, pain, often in muscles and joints, is distinguished by special symptoms. Human viruses that cause respiratory disease are usually active in the body for no more than a week. This means that approximately 3-5 days after the first symptoms, the patient feels a significant improvement in his condition.

With a bacterial infection, there is a strong fever, pain in the throat and chest, the discharge becomes greenish, yellow, thicker, and blood impurities can be observed. The immune system does not always successfully cope with bacteria, therefore, improvement in the condition in the first week of the disease may not be observed. Bacterial diseases of the respiratory tract can cause complications in the heart, lungs and other organs, so treatment should be started as soon as possible.

It is extremely difficult to identify a virus by symptoms alone. This is especially true of types of viruses that are similar in their effects on the body. For example, to date, about 80 human papillomaviruses have been studied. Some of them are quite safe, while others lead to the development of cancer. Hepatitis viruses, despite the fact that they affect the same organ, the liver, pose a different threat. Hepatitis A often goes away without complications, and the C virus, on the contrary, in 55-85%, according to WHO, leads to the development of a chronic disease that ends with cancer or cirrhosis of the liver. Therefore, if symptoms are detected or if an infection is suspected, it is necessary to pass tests that will help to accurately determine the type of virus.

Virus analysis

Among the analyzes that are used to detect viruses, the most popular are:

• Immunoassay blood test.

It is used to detect antigens and antibodies to them. In this case, there is both a qualitative (determination of the presence of a virus) and quantitative (determination of the number of virions) analysis. Also, this method will help determine the level of hormones, identify sexually transmitted infections, allergens, etc.

• Serological blood test.

It is used not only to determine an infectious disease, but also to establish its stage.

• Polymerase chain reaction (PCR method).

To date, the most accurate method that helps to identify even small fragments of foreign genetic material in the blood. Moreover, since this analysis for viruses determines the presence of the pathogen, and not the reaction to it (detection of antibodies), it can be carried out even in the incubation period of the disease, when there is still no noticeable immune response.

To diagnose viral infections, it is important to determine not only the infection itself, but also its amount in the blood. This is the so-called viral load - the amount of a specific type of virus in a specific volume of blood. It is thanks to this indicator that doctors determine the infectiousness of a person, the stage of the disease, can control the treatment process and check its effectiveness.

After the virus enters the human body, the immune system begins to produce specific immunoglobulins (Ig) - antibodies to a specific type of virus. It is by them that it is often possible to reliably determine a specific disease, the stage of the disease, and even the presence of a previous infection.

In humans, there are five classes of antibodies - IgG, IgA, IgM, IgD, IgE. However, in the analysis for the virus, two indicators are most often used:

• IgM - immunoglobulins, which are produced first when an infection enters. That is why their presence in the blood speaks of the acute stage of a viral infection. IgM are produced throughout the disease, with primary infection or exacerbation. These are large enough immunoglobulins that, for example, cannot pass through the placental barrier. This explains the serious damage to the fetus by some viruses during the initial infection of a woman during pregnancy.
• IgG - antibodies to the virus, which are produced much later, in some diseases, already at the stage of recovery. These immunoglobulins are able to remain in the blood for life and thus provide immunity against a particular virus.

Antibody tests should be deciphered as follows:

• IgM and IgG are absent. There is no immunity, the person has not encountered an infection, which means that primary infection is possible. When planning pregnancy, such indicators for certain viruses in women mean a risk group for developing a primary infection. In this case, vaccination is recommended.
• IgM is absent, IgG is present. The body has developed immunity to a specific virus.
• IgM is present, IgG is absent. There is an acute stage of infection, the virus is in the body for the first time.
• IgM and IgG are present. The end of the disease, or the exacerbation of a chronic process. The correct interpretation of such a virus test result depends on the amount of antibodies and can only be done by a doctor.

Types of viral infections

Viruses, like other antigens, cause an immune response - this is how the body copes with various foreign objects and microorganisms. However, some types of viruses can remain invisible for a long time to the immune system. It depends on this how long the disease will last, whether it will turn into a chronic form, and what harm it can inflict on the body.

Any viral disease begins with an acute stage. However, in some cases, after it, recovery occurs, and in others, the disease becomes chronic. Moreover, many diseases prone to chronicity are extremely weak in the acute period. Their symptoms are nonspecific and sometimes completely absent. On the contrary, those diseases that the immune system successfully suppresses are characterized by severe symptoms.

Acute viral infections that do not become chronic include:

• ARVI, including influenza
• Rubella
• Parotitis
• Hepatitis A (Botkin's disease) and E
• Rotavirus infection (intestinal flu)
• Chicken pox

Persistent immunity is developed to the listed viruses in the human body. Therefore, diseases are transferred only once in a lifetime. The only exceptions are some forms of ARVI, in particular, influenza, the virus of which is actively mutating.

Chronic viral infections

A considerable number of viruses are characterized by a chronic course. Moreover, in some cases, if a virus is detected, then after the acute stage the person remains its lifelong carrier. That is, the infection does not pose a danger to human health and life. These viruses include:

• Epstein-Barr virus (in rare cases, it can cause infectious mononucleosis).
• Some types of human papillomavirus.
• Herpes simplex virus types 1 and 2.

All these viruses are potentially capable of causing quite serious damage to tissues and systems, but only if the immunity is significantly reduced. For example, with AIDS, some autoimmune diseases, as well as when taking certain medications, in particular, in the treatment of cancer.

Another group of viruses that can remain in the human body for life is dangerous even for people with a normally functioning immune system. Among the main infections of this kind:

• AIDS virus.

The period of infection and the first stage of the spread of the virus throughout the body is asymptomatic. However, 2-15 years after infection, a person develops acquired immunodeficiency syndrome (AIDS). It is the syndrome that causes deaths among HIV-infected.

• Hepatitis C and B.

Hepatitis C in the acute stage is asymptomatic, and often (up to 85%) becomes chronic, which threatens with serious complications in the form of cancer or cirrhosis of the liver. However, today there are drugs that are quite effective in curing patients. Hepatitis B becomes chronic much less frequently, in no more than 10% of cases in adults. At the same time, there is no cure for this virus - chronic hepatitis B is not treated.

• Human papillomavirus with high cancer risk (types 16, 18 and others).

Some types of HPV are capable of provoking the development of malignant tumors, in particular, it is the human papillomavirus in women that causes 70% of all cases of cervical cancer. The virus in men can also manifest itself by the formation of warts of various types, but does not cause cancer.

To date, medicine has made significant progress in the treatment of viral infections, but this group of diseases is difficult to treat. In most cases, there are simply no effective drugs, and the treatment of viruses is reduced to symptomatic and supportive therapy.

What to do if a virus is found

The treatment strategy is determined by which virus is detected. For example, if we are talking about ARVI, childhood viral diseases (measles, rubella, mumps, baby roseola), the removal of symptoms will be an effective therapy. And only if they cause significant discomfort. So, for example, you can apply:

• Vasoconstrictor drops to relieve swelling in the nasal cavity.
• Antipyretic at high temperatures (from 37.5-38 ° C).
• Non-steroidal anti-inflammatory drugs that have a double effect - they lower the temperature and relieve pain (ibuprofen, paracetamol, aspirin).

Treatment of the influenza virus does not differ from the described scheme, however, since it is this infection that often causes severe complications, the patient must be under medical supervision. One of the most dangerous consequences is viral pneumonia, which develops on the 2-3rd day after the onset of the disease and can cause pulmonary edema and lead to death. Such pneumonia is treated exclusively in a hospital with the use of specific drugs (Oseltamivir and Zanamivir).

If human papillomavirus is detected, treatment is limited to supportive therapy and surgical removal of genital warts and warts.

With hepatitis C in the chronic stage, modern medicine uses direct-acting antiviral drugs (DPA). It is these drugs that WHO recommends today, as an alternative to interferons and Ribavirin, with which the disease was treated until recently.

People with HIV are prescribed antiretroviral therapy. If a virus is found in the body, it cannot be completely eliminated, but thanks to treatment it is possible to keep it under control and also prevent the spread of the disease.

With an exacerbation of herpes infection, special medications can be taken, but they are effective only in the first 48 hours after the onset of symptoms. Their use later is impractical.

The basis of the fight against viruses in the body is human immunity. It is he who provides a successful cure for most of the known viruses, while others are able to neutralize, make them safe.

The immune system is quite complex and multi-stage. It is divided into innate and acquired immunity. The first provides non-specific protection, that is, it acts on all foreign objects in the same way. The acquired one appears after the immune system encounters a virus. As a result, a specific defense is developed that is effective in the event of a specific infection.

At the same time, some viruses in one way or another are able to resist the defense system and not cause an immune response. A striking example is HIV, which infects the cells of the immune system itself; these viruses are successfully isolated from them and block the production of antibodies.

Another example is neurotropic viruses that infect cells in the nervous system, and the immune system simply cannot get to them. These infections include rabies and polio.

Congenital immunity

Congenital immunity is the body's reaction to any foreign biomaterial that occurs at the first contact with an infection. The reaction develops very quickly, however, unlike acquired immunity, this system recognizes the type of antigen worse.

Congenital immunity can be divided into components:

• Cellular immunity.

Most of it is provided by phagocyte cells capable of absorbing the virus, infected dying or dead cells. Phagocytosis is an important component of post-infectious immunity. In fact, it is phagocytes that are responsible for the effective cleansing of the body from foreign objects.

• Humonal immunity.

An important defense response to viral diseases is the body's ability to produce a specific protein, interferon. The affected cell begins to produce it as soon as the virus begins to multiply in it. Interferon is released from the infected cell and comes into contact with neighboring healthy cells. The protein itself has no effect on the virus, so infectious agents cannot develop a defense against it. However, it is interferon that can change unaffected cells in such a way that they suppress the synthesis of viral proteins, their assembly and even the release of virions. As a result, cells become immune to the virus, prevent it from multiplying and spreading throughout the body.

Acquired immunity

Acquired immunity is the ability to neutralize antigens that have already entered the body earlier. Distinguish between active and passive types of innate immunity. The first is formed after the body encounters a virus or bacterium. The second is passed on to the fetus or infant from the mother. Through the placenta during pregnancy and with breast milk during breastfeeding, antibodies from the mother's blood pass to the baby. Passive immunity provides protection for several months, active - often for life.

Acquired immunity, as well as innate immunity, can be divided into:

• Cellular immunity.

It is provided by T-lymphocytes (a subtype of leukocytes) - cells that are able to recognize viral fragments, attack and destroy them.

• Humonal immunity.

The ability of B-lymphocytes to produce antibodies to the virus (immunoglobulins), which neutralize specific antigens, allows the body to create specific defenses. An important function of humonal immunity is the ability to remember contact with an antigen. For this, specific IgG antibodies are produced, which are subsequently able to prevent the development of the disease if a virus is infected.

To date, a relatively small number of antiviral drugs with proven effectiveness are used in medicine. The entire spectrum of drugs can be divided into two groups:

1. Stimulating the human immune system.
2. Acting directly on the detected virus, the so-called direct-acting drugs.

The first can be called drugs wide range actions, however, their treatment often has a number of serious complications. Interferons are one of these drugs. The most popular of them is interferon alpha-2b, which is used in the treatment of chronic forms of hepatitis B and was previously used for the hepatitis C virus. Interferons are quite difficult to tolerate by patients, often causing various side effects from the cardiovascular and central nervous system. They also impose pyrogenic properties - they cause fever.

The second group of antiviral drugs is more effective and easier to tolerate by patients. Among them, the most popular are medicines that treat:

• Herpes (Acyclovir drug).

Suppress the symptoms of viral disease, but cannot completely eliminate the virus.

• Flu.

On the recommendation of the WHO, inhibitors of influenza neuraminidase (Oseltamivir and Zanamivir) are now being used, since most modern strains of the influenza virus have resistance to their predecessors, adamants. The commercial names of the drugs are Tamiflu and Relenza.

• Hepatitis.

Until recently, Ribavirin in combination with interferons was actively used to treat hepatitis C and B. Now hepatitis C (genotype 1B) is treated with new generation medicines. In particular, since 2013, the direct-acting drug Simeprevir has been approved, which has shown high efficiency - 80-91% of a persistent virological response in different groups, including 60-80% in people with liver cirrhosis.

Unfortunately, drugs cannot completely eliminate the virus, but antiretroviral drugs give a fairly stable effect - the stage of remission begins, and the person becomes non-infectious to others. For HIV-positive people, antiretroviral therapy must be lifelong.

Prevention of viral diseases

Since there is no specific treatment for many viral diseases, but at the same time they pose a very real danger to human health and life, prevention comes to the fore.

Precautionary measures

Many viral infections spread quickly and are highly contagious. When it comes to viruses transmitted by airborne droplets, an effective measure is the introduction of quarantine in preschool and school institutions. Because an infected child can spread the virus even before symptoms appear, this is how the whole community can be prevented from getting the virus.

In an epidemically dangerous period, it is advisable to avoid large crowds of people, especially in closed rooms. This will reduce the risk of contracting various acute respiratory viral infections, including the flu.

Prevention of viruses transmitted by the fecal-oral route (for example, Botkin's disease and poliomyelitis) - washing hands, boiling water and using only proven water sources, thoroughly washing fruits and vegetables.

The most dangerous are viruses transmitted through blood and other biological fluids. Risk factors for infection for them are:

• Injection drug addiction.
• Beauty treatments and tattooing using non-disinfected instruments.
• The use of personal hygiene items of an infected person - nail scissors, toothbrush, razor, and more.
• Unprotected sex.
• Surgery, blood transfusion.

A person who is at risk of being infected with such diseases must be tested for antibodies to viruses, primarily HIV, hepatitis C and B. It is necessary to donate blood 4-5 weeks after the alleged infection.

Any precautions do not guarantee 100% virus protection. To date, the most reasonable way to prevent viral infections is vaccination.

Pharmacists have developed vaccines that are effective against more than 30 different viruses. Among them:

• Measles.
• Rubella.
• Mumps.
• Chicken pox.
• Flu.
• Polio.
• Hepatitis B.
• Hepatitis A.
• Human papillomavirus 16 and 18 types.

It was with the help of mass vaccination that it was possible to defeat the two variola viruses, which caused epidemics and led to death and disability.

Since 1988, WHO has partnered with a number of public and private health sectors to launch the Global Polio Eradication Initiative. To date, it is with the help of mass immunization that it has been possible to reduce the number of cases of infection with the virus by 99%. As of 2016, polio is endemic (that is, one that does not go beyond the country) in only two countries - Afghanistan and Pakistan.

The following material is used in vaccines:

• Live but weakened microorganisms.
• Inactivated - killed viruses.
• Acellular - purified material, such as proteins or other parts of the antigen.
• Synthetic components.

In order to reduce the risk of complications, vaccination for some viruses takes place in several stages - first with inactivated material, and then with live material.

Some vaccines give immunity for life - resistant antibodies to the virus are produced. Others require revaccination - a booster shot after a certain time.

Viruses and diseases

Human viruses cause diseases of various severity and course. Some of them are encountered by most of the inhabitants of the earth, others are rare. In this section, we have collected the most famous viruses.

Adenovirus

Adenovirus was discovered in 1953, then it was discovered after surgery on the tonsils and adenoids. Today, science knows about 50-80 subspecies of this virus, and they all cause similar diseases. It is the adenovirus that is a common cause of the development of acute respiratory viral infections, and also in some cases can lead to intestinal diseases in children. Infection with the virus leads to damage to the cells of the mucous membranes of the upper respiratory tract, tonsils, eyes, bronchi.

• Transmission path.

Airborne (more than 90% of cases), fecal-oral.

• Virus symptoms.

The disease begins with a high fever, which can rise to 38 ° C. General intoxication appears - chills, pain in muscles, joints, temples, weakness. There is a reddening of the throat and inflammation of the laryngeal mucosa, as well as rhinitis. In case of eye damage - redness of the mucous membranes, itching, pain.

• Potential complications.

They rarely appear, a bacterial infection may join, which will cause pneumonia, otitis media, sinusitis.

• Treatment.

Symptomatic, the use of vitamins, antihistamines is permissible.

• Forecast.

Favorable, in the absence of concomitant diseases and immunodeficiency, the disease goes away on its own.

The influenza virus is perhaps the best known of all respiratory infections. It really differs from other acute respiratory viral infections both in symptoms and in possible complications.

It is the flu that often causes epidemics and pandemics, as the virus constantly mutates. Moreover, some strains are capable of leading to quite serious diseases, often fatal. Every year, even in the absence of serious pandemics, according to WHO, from 250 thousand to 500 thousand people die in the world.

• Transmission path.

Airborne, the virus can also persist on the surfaces and hands of an infected person.

• Virus symptoms.

It always begins acutely - the temperature rises (sometimes up to 39 ° C), cough and rhinitis begin, the general condition worsens. The influenza virus causes severe intoxication of the body, which manifests itself in pain, general weakness, drowsiness, and loss of appetite.

• Potential complications.

Influenza more often than other acute respiratory viral infections leads to complications, most of which are associated with the addition of a bacterial infection - pneumonia, bronchitis, otitis media, sinusitis and other diseases. Intoxication leads to exacerbation of chronic diseases, including cardiovascular, diabetes, asthma. Influenza can also cause viral complications, which appear 2-3 days after the first symptoms. These are the most dangerous consequences of the disease, as they can lead to pulmonary edema, the development of encephalitis and meningitis. Temporary loss of hearing or smell may occur.

• Treatment.

In the normal course of the disease, the detected virus does not need specific treatment. With the development of viral complications, especially pneumonia, the drugs Oseltamivir and Zanamivir are used, and interferons may be administered.

• Forecast.

The greatest danger from influenza is for people over 65 years of age, as well as those who have concomitant diseases - diabetes, heart and lung diseases. It is among these categories that the virus is most often fatal. Also, infection with the influenza virus can be dangerous for pregnant women and children. Therefore, for people at risk, WHO recommends getting an annual vaccination.

Chickenpox (chickenpox) is caused by the human herpesvirus type 3 from a wide family of herpes viruses. This disease is typical for young children, the person who underwent it gains immunity to the virus for life. In this case, the body's susceptibility is 100%. Therefore, if a person without acquired immunity contacts a sick person, he will definitely become infected. In adulthood, chickenpox can be more difficult to tolerate, and if the primary infection occurred in a pregnant woman, it can cause serious fetal damage (however, in a maximum of 2% of cases).

• Transmission path.

Airborne, while the virus is able to move with the air current at distances up to 20 m.

• Virus symptoms.

The main distinguishing feature of chickenpox is a specific blistering rash that spreads throughout the body, occurs on the mucous membranes. After the first symptoms, new bubbles form for another 2-5 days, in rare cases up to 9 days. They itch and itch. The onset of the disease is accompanied by a high fever, which is especially difficult in adults.

• Potential complications.

In childhood, chickenpox is easily tolerated, the infection goes away on its own without specific treatment. Particular attention should be paid to the rash, because if it is combed, a scar may form on the skin. Also, bursting vesicles and ulcers that have arisen in their place can be an entrance for a bacterial skin infection.

• Treatment.

There is no specific treatment, with chickenpox, treatment is symptomatic, in particular, prevention of skin infection is carried out. An effective vaccine has now been developed against the virus, which provides lifelong immunity.

• Forecast.

Favorable.

Herpes simplex virus

There are two types of herpes simplex virus. The first type most often causes sores on the lips and mucous membranes of the mouth. The second is genital lesions. A person who has contracted the herpes virus remains its carrier for life. This infection cannot be cured, but with normal immunity it can be asymptomatic. HSV belongs to neurotropic viruses, that is, after infection, it moves to nerve cells and there it remains inaccessible to the immune system.

The greatest danger is posed by HSV-2, since, according to the WHO, it increases the risk of infection with the human immunodeficiency virus by 3 times.

• Transmission path.

HSV-1 is transmitted through oral contact, with saliva, during an exacerbation of the infection. HSV-2 is transmitted sexually and vertically.

• Virus symptoms.

HSV-1 is manifested from time to time by the formation of ulcers on the lips and mucous membranes. The frequency of such rashes depends on the person's immunity; in some cases, the carrier may not show the virus at all. HSV-2 is also often asymptomatic, sometimes manifested by rashes in the form of vesicles on the genitals and in the anal region.

• Potential complications.

The most dangerous type 2 virus in women is during pregnancy, since it can cause infection of the fetus and subsequent pathologies from the central nervous system and other organs.

• Treatment.

In case of exacerbations, the use of antiherpetic drugs, such as acyclovir, may be recommended to an infected person.

• Forecast.

In the absence of immunodeficiency, this infection does not lead to serious health problems.

The papillomavirus group combines more than 100 types of various extracellular agents. Despite the fact that they cause diseases that are similar in symptoms - neoplasms appear on the skin - the severity of the course of the disease depends on the type of infection, as well as the immune system of the infected person.

Human papillomavirus

Human papillomaviruses (HPV) are one of the most common infections in the world that can cause various lesions. Most species are harmless, show mild symptoms after infection and then go away without treatment. According to the WHO, 90% are completely cured within 2 years after infection.

However, the human papillomavirus is still under special control and is being studied in detail. This is due to the fact that today it has been proven that at least 13 types of human papillomavirus are capable of causing cancer. First of all, types 16 and 18 are dangerous.

• Transmission path.

Contact (through the skin with a neoplasm), sexual (for genital forms of the virus).

• Virus symptoms.

After infection, papillomas, condylomas and various warts form on the skin or mucous membranes. Depending on the type of HPV, they look different and occur on different parts of the body. So, for example, for some types (1, 2, 4), lesions of the feet are characteristic, the oral mucosa is attacked by viruses of types 13 and 32. Condylomas on the genitals arise under the influence of 6, 11, 16, 18 and other types.

• Potential complications.

The most dangerous complication is the transformation of the papilloma into a malignant tumor.

• Treatment.

There is no specific therapy. Viruses either go away on their own, or remain for life. Surgical removal of warts, genital warts and papillomas is recommended for people with severe symptoms.

• Forecast.

Overall favorable. Even HPV types with a high cancer risk can be controlled. The key to the successful suppression of human papillomavirus in women and men is timely diagnosis, which involves blood tests for antibodies.

Human papillomavirus in women

The relationship of some types of human papillomavirus in women with the development of cervical cancer has been proven. According to the WHO, 16 and 18 types cause 70% of all cases of this cancer.

At the same time, it takes an average of 15-20 years for a neoplasm to degenerate, if a woman has no problems with immunity. For HIV-infected, this interval can be 5 years. Local treatment can help prevent the development of infection, and this requires timely diagnosis. That is why women are recommended to undergo annual examinations by a gynecologist and be tested for papilloma viruses.

On the genitals, two types of genital warts develop - pointed and flat. The former most often provoke virus types 6 and 11. They are clearly visible, form on the external genitals, and rarely lead to cancer. Flat viruses are provoked by viruses of types 16 and 18. They are located on the internal genital organs, are less visible and have a high risk of cancer.

Today, vaccines have been developed for 16 and 18 HPVs, which WHO recommends for use at the age of 9-13 years. In the United States and some European countries, these vaccinations are included in the vaccination schedule.

Among all liver inflammations, diseases of a viral nature are most common. There are such types of hepatitis viruses - A, B, C, D and E. They differ in the mode of transmission, course of the disease and prognosis.

Hepatitis A and E

Viruses of this group differ from the rest in that they are not capable of causing chronic disease. In the vast majority of cases, a once transferred illness gives lifelong immunity. Therefore, Botkin's disease is characteristic of childhood.

• Transmission path.

Alimentary (fecal-oral), most often through contaminated water.

• Virus symptoms.

Hepatitis A and E is manifested by nausea, vomiting, pain in the liver, fever, loss of appetite. Darkening of urine and whiteness of feces are also characteristic. The disease includes an icteric period, in which, due to an increase in the level of bilirubin in the blood, the skin, mucous membranes, nail plates and sclera of the eyes acquire a yellow tint.

• Potential complications.

These liver inflammations are dangerous for people with immunodeficiency disorders and also during pregnancy. In case of infection with the virus during pregnancy, hepatitis A is much more difficult to carry, and hepatitis E can cause serious fetal abnormalities and, in some cases, death of the mother.

• Treatment.

There is no specific treatment for hepatitis A and E viruses. The main therapy consists of supportive measures and adherence to a therapeutic diet. A vaccine has been developed against hepatitis A.

• Forecast.

Favorable. Hepatitis A and E viruses do not cause chronic disease. The infection goes away without treatment after a few weeks or months. In the future, the liver is able to fully recover.

Hepatitis B, C, D

Hepatitis B, C and D pose a great health hazard. They are prone to chronicity, especially type C, which leads to chronic disease in 55-85% of cases. The hepatitis D virus is particularly dangerous. This is a satellite virus, that is, one that is active only in the presence of virus B. It is he who significantly aggravates the course of the disease. And in some cases, coinfection leads to acute liver failure and death already in the acute period of the disease.

• Transmission path.

Hematogenous (through blood), sexual, vertical. Hepatitis B, which is sometimes called serum hepatitis, is especially contagious.

• Symptoms

Hepatitis B is acute with severe symptoms of liver damage - intoxication, nausea, loss of appetite, white feces, dark urine, jaundice. Hepatitis C in the acute stage in the vast majority of cases is asymptomatic. Moreover, it can remain invisible and chronic. A person guesses about the disease only at the critical stages of cirrhosis or liver cancer.

• Potential complications.

Both diseases can develop into chronic infections. Most often this occurs in the case of the hepatitis C virus. The chronization of hepatitis B depends on the patient's age. So, for example, in infants the probability of such a course is 80-90%, and for adults - less than 5%. Chronic hepatitis is dangerous by irreversible liver damage - cirrhosis, cancer, acute liver failure.

• Treatment.

Hepatitis B is treated in the acute period; in the chronic form, there is no specific therapy - lifelong maintenance drugs are prescribed. However, there is an effective vaccine against the B virus, which has been used since 1982. Modern pharmacological developments have made it possible to increase the percentage of treatment efficiency for chronic hepatitis C up to 90%. Currently, direct-acting antiviral drugs are used for this disease, which are taken for 12 weeks.

• Forecast.

Chronic hepatitis C can cause serious liver damage for 20 years after infection, in some cases for 5-7 years. The risk of developing cirrhosis is 15-30%. Hepatitis B is already dangerous in the acute period if the virus D is also present in the blood. Chronic hepatitis B can also cause serious liver damage.

Human Immunodeficiency Virus (HIV)

HIV is considered one of the most dangerous infections in the world today. It is ubiquitous; as of 2014, there were approximately 37 million infected people worldwide. HIV is a pandemic disease that differs from others in that it attacks the immune system itself. The virus is most dangerous in the final stage of the disease - with acquired immunodeficiency syndrome (AIDS). It is with such a diagnosis that other infections can become active in a person, there is a tendency to the formation of malignant tumors, any minor illness gives serious complications. It is a strong decrease in immunity that is the cause of death from HIV.

• Transmission path.

Hematogenous, sexual.

• Symptoms

Until the development of AIDS, it is asymptomatic. After there are manifestations of lowered immunity, in particular, viruses are activated, which practically do not manifest themselves in a healthy person. For example, the Epstein-Barr virus, cytomegalovirus. Other viruses (measles, rubella, influenza,) lead to serious injuries and the development of pathologies.

• Potential complications.

Associated with infections that a person has. With immunodeficiency, the risk of developing complications in any disease sometimes reaches 100%. Even some mild infections can be fatal.

• Treatment.

HIV cannot be completely cured. If a person becomes infected, the infection will remain with him for life. However, effective antiretroviral therapy has been developed that must be lifelong. Thanks to these drugs, HIV can be kept under control, preventing the development of AIDS. The viral load is reduced so much that the person receiving treatment is no longer infectious.

• Forecast.

With timely treatment started, HIV-positive people are able to live a fulfilling life. Without treatment, AIDS develops within 2-15 years and leads to the death of the patient.

Cytomegalovirus infection is often remembered in the context of diseases that are dangerous during pregnancy. It is for the fetus that this virus from the herpesvirus family can pose a serious threat. However, this happens only if a woman becomes infected while carrying a child. This happens quite rarely, because the majority of the population is faced with the virus as early as childhood.

• Transmission path.

Through biological fluids - saliva, urine, semen, secretions, and also through breast milk.

• Virus symptoms.

In people without immunodeficiency, even in the acute period, it is asymptomatic. The fetus may develop various pathologies, in particular deafness. Primary infection with cytomegalovirus during pregnancy can lead to miscarriage.

• Potential complications.

It is extremely rare and only for risk groups.

• Treatment.

A vaccine has been developed against cytomegalovirus, which may be necessary for people with immunodeficiency, pregnant women without acquired immunity to the virus.

• Forecast.

Favorable.

Rabies virus

The rabies virus is a neurotropic virus, that is, those that are capable of infecting nerve cells. Being in the nervous system, it becomes inaccessible to the cells of the immune system, since the immune response acts only within the bloodstream. That is why infection with rabies without treatment is fatal.

• Transmission path.

Through the bites and saliva of infected animals. Most commonly transmitted from dogs.

• Virus symptoms.

After the incubation period, which lasts an average of 1-3 months, there is a slight increase in temperature, pain at the site of the bite, and insomnia. Later, convulsions, phobia and hydration, hallucinations, fear, aggression appear. The disease ends with muscle paralysis and breathing disorders.

• Potential complications.

If symptoms appear, rabies is fatal.

• Treatment.

Vaccination should be started immediately after a bite or possible contact with a rabid animal. Treatment for rabies virus consists of a course of post-exposure prophylaxis (PEP).

• Forecast.

With timely vaccination, it is favorable.

Poliomyelitis mainly affects children under 5 years of age. In most cases, it does not cause serious health consequences, but 1 in 200 people infected with the virus causes severe paralysis. In 5-10% of patients with complications, paralysis of the respiratory muscles also occurs, which leads to death.

Polio has now been virtually eradicated by vaccination. This disease remained endemic in two countries - Pakistan and Afghanistan.

• Transmission path.

Fecal-oral.

• Virus symptoms.

With a paralytic form of the course of the disease, the body temperature rises, a runny nose, nausea, and headache appear. Paralysis can develop over several hours, most often affecting the limbs.

• Potential complications.

Muscle atrophy, deformity of the trunk, persistent paralysis of the limbs that remain for life.

• Treatment.

There is no specific treatment. At the same time, vaccination against poliomyelitis completely eliminates the risk of infection.

• Forecast.

Due to the immunization of the population, the number of pathologies caused by poliomyelitis has decreased by 99% since 1988.