Viral diseases - a list of common ailments and the most dangerous viruses. Deadly nine: the most terrible infections in the world

non-cellular infectious agent. It has a genome (DNA or RNA), but is deprived of its own synthesizing apparatus. Able to reproduce, only getting into the cells of more highly organized creatures. Reproducing, damages the cells in which this process occurs.

Each of us is faced with viruses many times in life. After all, they are the cause of most cases of seasonal colds. With the usual ARVI, the body successfully copes on its own - our immunity steadfastly withstands the blows 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, cause disability and even death. How to understand the diversity of viruses? How to protect yourself from the most dangerous? And what if the disease is already detected? What are antibodies to the virus and which ones appear during the illness?

Human viruses

To date, more than 5,000 different viruses have been described, but it is estimated that there are millions of their species. They are found in all ecosystems and are considered the most numerous biological form. At the same time, 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, diseases are very diverse in their severity, prognosis and course.

At the same time, an important condition of evolution is associated with viruses - horizontal gene transfer, in which the genetic material is transferred not to descendants, but to other types of organisms. In fact, the virus has provided a great deal of genetic diversity. For example, studies have shown that 6-7% of the human genome consists 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 paramyxovirus, which causes mumps. Most often, the mumps passes without any 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 in 68% of cases it can cause orchitis - inflammation of the testicles. And this, in turn, can lead to 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 the best protection against the disease is vaccination. The mumps vaccine 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 of its species 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 types 16 and 18, which are characterized by the highest oncological risk, are the most dangerous. 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, this outcome can be avoided. Cancer, as a complication of HPV, develops within 15-20 years with normal immunity, so systematic examinations by a gynecologist will help to identify a dangerous virus in women of different ages in time. It should be said that such a factor as smoking affects the activity of the papillomavirus - 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 are especially dangerous in women during pregnancy, because due to their small size they easily penetrate the placental barrier. At the same time, the severity of the course of the disease in the mother and the likelihood of damage to the fetus 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 produce enough antibodies to protect the fetus, and the virus causes serious damage.

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

Viruses transmitted through the blood and its components, as well as other biological fluids, are also dangerous directly during childbirth. Since the child 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 probability of fetal damage is 80%. After 16 weeks, the risk of damage 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 1st (HSV-1) and 2nd (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 is possible, among which encephalitis is the most dangerous. In some cases, the herpes virus type 2 can lead to the death of 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 that are incompatible with life, resulting in a miscarriage. In addition, the disease is dangerous not only by the influence of the virus itself, but also by general intoxication of the body. It, in turn, can cause fetal hypoxia, developmental delay and other things. That is why WHO recommends that pregnant women be vaccinated against influenza, especially during an epidemically dangerous period.

Botkin's disease (hepatitis A) is very often transferred in childhood, so it is quite rare during pregnancy. However, if infection does occur, the disease will proceed in a severe form. Hepatitis B and C can pose a threat to the unborn child, especially if a woman has contracted them during pregnancy. Chronic hepatitis B and C are dangerous infection during childbirth. Most often, it is the hepatitis B virus that is transmitted in this way. Moreover, in the congenital form, it is treated much more difficult and in 90% of cases it passes into a chronic incurable form. Therefore, women planning a pregnancy may be recommended to be vaccinated against hepatitis B. If there is a chronic infection, then it is worth doing a caesarean section. The hepatitis E virus is rarely 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 the 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 bearing of a child, the fetus in 7% of cases can receive 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 SARS (acute respiratory viral infections) more often than an adult. The frequency of infection with the virus at different ages is the same, 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 that suffers more than 5 SARS per year. However, foreign doctors believe that for children under 3 years old, the norm is 6 infections per year. And a child attending kindergarten can endure up to 10 colds annually. If SARS pass without complications, they should not cause concern, - the well-known pediatrician Yevgeny Komarovsky also believes so.

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

• Chickenpox.
• Measles.
• Rubella.
• Mumps.

At the same time, 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 main causes of child mortality, and mumps causes inflammation in the genitals. Therefore, there are effective vaccinations against all of the above viral infections - timely immunization makes it possible to receive immunity without a previous illness.

Virus as a form of life

Also, these non-cellular infectious agents, which 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, and not a microorganism. A virus outside of a cell is called a virion. This 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 transferring its genetic code to new virions.

Viruses, like other living organisms, are able to evolve through natural selection. It is due to this that some of them, such as the influenza virus, are able to constantly cause epidemics, since the developed immunity against new forms does not work.

The size of the virion 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 also 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 inside 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 possible only inside the cell.

• The release of virions from the host cell.

In this case, the membrane and cell wall are damaged, and the cell itself dies. However, in some cases, viruses remain in the cell without damaging it and multiply 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, for 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, they are usually divided into DNA-containing and RNA-containing (Baltimore classification).

• DNA containing viruses.

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

• RNA viruses.

A large group that mainly multiplies in the cytoplasm of the cell. Among RNA-containing agents, one should separately mention retroviruses, which differ from others in that they are able to integrate into the DNA of the host cell. These viruses are often separated into a separate group for their unique reverse transcription property. During normal genome replication, information passes 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 classified as a retrovirus. On the other hand, it was precisely this 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 the species diversity of living organisms, as well as evolutionary processes, with them.

Types of viruses

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

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

• Nucleic acid (RNA or DNA).
• Protein coat (capsid).
• Shell (supercapsid). It does not occur in all types of viruses.

Virus capsid

The outer shell consists of proteins and performs a protective function of the genetic material. It is the capsid that determines which types of cells the virion can attach to, the shell is also responsible for the initial stages of cell infection - membrane rupture and introduction.

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

In total, 4 types of capsids are distinguished, which are easy to distinguish by 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 can infect animal cells, and therefore infect 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 type. Occurs rarely.

Virus shell

Some types of viruses, for additional protection, surround themselves with another shell 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 an envelope, essentially consisting of material related to the body, makes the virus less visible to the human immune system. This means that such vibrios are highly contagious, able to stay in the body longer than others like them. Examples of enveloped virions are HIV and the influenza virus.

Virus infection

Signs of the presence of a virus in the body are highly dependent on its type. 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.

Methods of infection with viruses

Since viruses are widespread and capable of infecting different cells of the human body, all the main ways of transmitting infection are available to them:

• Airborne (airborne) - viruses are carried through the air, when coughing, sneezing, or even just talking.

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

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

Infection occurs through dirty water, poorly washed food or dirty hands. Examples are hepatitis A and E, poliomyelitis. Often, such infections are characterized by a seasonal 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 transfusions, 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. Hepatitis B, C and D viruses, HIV, rabies and others are transmitted through the blood.

• Transmissible - transmitted through the bites of insects and ticks.

Among the most common diseases caused by such 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 contact.

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, papillomavirus, hepatitis B.

Not all viruses that enter the human body are capable of causing disease. Any foreign organism that comes to us immediately meets with 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 have developed. Our immune system gives stable protection, often for life, to many viruses - acquired immunity is developed after contact with the virus (illness, vaccination).

Some infections, such as measles, rubella, poliomyelitis, 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 “herd immunity” is provided with the help of vaccination, such viruses will not be able to cause epidemics in children's groups.

Some species, such as the influenza 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. This is, first of all, the "Spanish flu" of 1918-1919, which claimed 40-50 million lives, and the Asian flu of 1957-1958, during which approximately 70 thousand people died.

Smallpox viruses have also caused pandemics, causing between 300 and 500 million deaths in the 20th century alone. Thanks to mass vaccination and revaccination, this virus was defeated - the last case of infection was recorded in 1977.

Human immunodeficiency virus (HIV), which is also equivalent to a pandemic disease in terms of prevalence, causes serious concern.

Symptoms of the entry of the virus into the body

Different viruses in the body behave differently, manifest their 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 in an advanced stage or by chance - according to blood tests. Influenza, on the contrary, always proceeds acutely, with fever, general intoxication of the body. For measles and rubella, a specific rash on the skin is characteristic.

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 lifelong 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 warts is an occasion to take a virus test, 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 is still manifested by similar symptoms. SARS is characterized by:

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

Influenza is distinguished by special symptoms, which always begins acutely, within a few hours, is characterized by high fever, as well as general intoxication of the body - severe malaise, pain, often in muscles and joints. Human viruses that cause respiratory diseases are usually active in the body for no more than a week. And this means that approximately on the 3-5th day 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, blood impurities may be observed. The immune system does not always successfully cope with bacteria, so there may not be improvement in the first week of illness. Bacterial diseases of the respiratory tract can cause complications in the heart, lungs and other organs, so their treatment should be started as soon as possible.

It is extremely difficult to identify the virus only by symptoms. This is especially true for types of viruses that are similar in effect on the body. For example, about 80 human papillomaviruses have been studied to date. Some of them are quite safe, 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 passes without complications, and virus C, on the contrary, in 55-85%, according to WHO, leads to the development of a chronic disease ending in cancer or cirrhosis of the liver. Therefore, if symptoms are detected or if infection is suspected, tests should be taken to help accurately determine the type of virus.

Virus analysis

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

• ELISA blood test.

It is used to detect antigens and antibodies to them. At the same time, there is both a qualitative (determining the presence of a virus) and a quantitative (determining 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 virus test 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 particular type of virus in a certain volume of blood. It is thanks to this indicator that doctors determine the infectiousness of a person, the stage of the disease, they 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 one can often 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 are immunoglobulins that are produced first when an infection occurs. That is why their presence in the blood indicates an acute stage of a viral infection. IgM is produced throughout the course of the disease, during initial infection or exacerbation. These are rather large immunoglobulins, which, for example, cannot pass through the placental barrier. This explains the serious damage to the fetus by some viruses during the primary 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.

Analyzes for antibodies 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 a pregnancy, such indicators for certain viruses in women mean a risk group for the development of a primary infection. In this case, vaccination is recommended.
• IgM absent, IgG 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 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 are able to remain invisible to the immune system for a long time. It depends on this how long the disease will last, whether it will become chronic, and what harm it can cause to the body.

Any viral disease begins with an acute stage. However, in some cases, recovery occurs after it, and in others, the disease becomes chronic. Moreover, many diseases prone to chronicity are extremely weakly manifested 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:

• SARS, including influenza
• Rubella
• Mumps
• Hepatitis A (Botkin's disease) and E
• Rotavirus infection (intestinal flu)
• chickenpox

To the listed viruses in the human body, a strong immunity is developed. Therefore, diseases are transferred only once in a lifetime. The only exceptions are some forms of SARS, in particular, influenza, the virus of which actively mutates.

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, 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 in the case when immunity is significantly reduced. For example, with AIDS, certain autoimmune diseases, as well as when taking certain medications, in particular, in the treatment of oncological lesions.

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 are asymptomatic. However, 2-15 years after infection, a person develops acquired immunodeficiency syndrome (AIDS). It is the syndrome that is the cause of death among HIV-infected people.

• 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 effectively cure patients. Hepatitis B becomes chronic much less frequently, in no more than 10% of cases in adults. At the same time, there are no drugs for this virus - chronic hepatitis B is not treated.

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

Some types of HPV can provoke the development of malignant tumors, in particular, it is the human papillomavirus that causes 70% of all cases of cervical cancer in women. The virus in men can also be manifested by the formation of warts of various types, but does not cause oncological diseases.

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 SARS, childhood viral diseases (measles, rubella, mumps, roseola children), effective therapy will be the removal of symptoms. And only if they cause significant discomfort. So, for example, you can use:

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

The 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 the supervision of a doctor. 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 death. Such inflammation of the lungs 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 care and surgical removal of genital warts and warts.

In chronic hepatitis C, modern medicine uses direct-acting antiviral drugs (DAAs). 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 treated with antiretroviral drugs. If a virus is found in the body, it cannot be completely eliminated, but with treatment it is possible to control it and also prevent the spread of the disease.

With an exacerbation of a herpes infection, special drugs 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 the human immune system. It is he who provides a successful cure for most known viruses, while others are able to neutralize and make 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, specific protection is developed that is effective in the case 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 the cells of the nervous system, and the immune system simply cannot get to them. These infections include rabies and polio.

innate immunity

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

Innate immunity can be divided into components:

• Cellular immunity.

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

• Humonal immunity.

An important protective reaction 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 ones. The protein itself has no effect on the virus, so infectious agents cannot develop protection 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, the cells become immune to the virus, preventing it from multiplying and spreading throughout the body.

acquired immunity

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

Acquired immunity, like innate immunity, can be divided into:

• Cellular immunity.

It is provided by T-lymphocytes (a subspecies of leukocytes) - cells that can recognize viral fragments, attack them and destroy them.

• Humonal immunity.

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

To date, a relatively small number of antiviral drugs with proven efficacy 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 former can be called broad-spectrum drugs, but their treatment often has a number of serious complications. One of these drugs are interferons. The most popular of them is interferon alfa-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 on the cardiovascular and central nervous system. They also impose pyrogenic properties - cause fever.

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

• Herpes (drug Acyclovir).

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

• Flu.

According to WHO recommendations, influenza neuraminidase inhibitors (oseltamivir and zanamivir) are now being used, since most modern strains of the influenza virus have resistance to their predecessors, adamantium. 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. Hepatitis C (genotype 1B) is currently being treated with a new generation of drugs. In particular, since 2013, the direct-acting drug Simeprevir has been approved, which showed 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 - a remission stage sets in, and the person becomes non-infectious to others. For HIV-positive people, antiretroviral therapy should 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 airborne viruses, an effective measure is the introduction of quarantine in preschool and school institutions. Since an infected child can spread the virus even before symptoms appear, this is how the entire community can be prevented from infecting the virus.

In an epidemically dangerous period, it is advisable to avoid large crowds of people, especially in enclosed spaces. This will reduce the risk of infection with various acute respiratory viral infections, including influenza.

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

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

• injection drug addiction.
• Cosmetic procedures and tattooing using non-disinfected instruments.
• Use of personal hygiene items of an infected person - nail scissors, toothbrush, razor and more.
• Unprotected sex.
• Surgery, blood transfusion.

A person at risk for infection with such diseases must be tested for antibodies to viruses, primarily HIV, hepatitis C and B. Blood must be donated 4-5 weeks after the alleged infection.

Any precautionary measures do not give a 100% guarantee of protection against viruses. 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.
• Chickenpox.
• 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 two smallpox viruses that caused epidemics and led to death and disability.

Beginning in 1988, WHO, in partnership with a number of public and private health sectors, launched the Global Polio Eradication Initiative. To date, it is through mass immunization that the number of cases of virus infection has been reduced by 99%. As of 2016, polio is endemic (that is, one that does not spread outside the country) in only two countries - Afghanistan and Pakistan.

Vaccines use:

• Live but weakened microorganisms.
• Inactivated - killed viruses.
• Acellular - purified material, such as proteins or other parts of an 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 - re-vaccination after a certain time.

Viruses and diseases

Human viruses cause diseases of varying severity and course. Some of them are faced 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, about 50-80 subspecies of this virus are known to science, and all of them cause similar diseases. It is adenovirus that is a common cause of acute respiratory viral infections, and 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 temperature, which can rise to 38 ° C. General intoxication appears - chills, pain in muscles, joints, temples, weakness. There is redness of the throat and inflammation of the mucous membrane of the larynx, as well as rhinitis. With eye damage - redness of the mucous membranes, itching, pain.

• Possible complications.

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

• Treatment.

Symptomatic, the use of vitamins, antihistamines is acceptable.

• Forecast.

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

The influenza virus is perhaps the most well-known of all infections that cause damage to the respiratory tract. It really differs from other acute respiratory viral infections both in terms of symptoms and possible complications.

It is the flu that often causes epidemics and pandemics, as the virus constantly mutates. At the same time, some strains can lead to quite severe diseases, often with a fatal outcome. 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 starts acutely - the temperature rises (sometimes up to 39 ° C), cough and rhinitis begin, and the general condition worsens. The influenza virus causes severe intoxication of the body, which manifests itself in pain, general weakness, drowsiness, loss of appetite.

• Possible 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 will appear on the 2-3rd day 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 is possible.

• 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, the introduction of interferons is possible.

• Forecast.

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

Varicella (chickenpox) is caused by the human herpesvirus type 3 from the large family of herpesviruses. This disease is typical for young children, the person who has undergone it receives immunity to the virus for life. In this case, the susceptibility of the body is 100%. Therefore, if a person without acquired immunity comes into contact with a sick person, he will definitely become infected. In adulthood, chickenpox can be more difficult to tolerate, and if the primary infection occurs in a pregnant woman, it can cause serious damage to the fetus (however, in a maximum of 2% of cases).

• transmission path.

Airborne, while the virus is able to move with 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 blisters 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 high fever, especially difficult in adults.

• Possible complications.

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

• 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

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

The greatest danger is HSV-2, since, according to 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 area.

• Possible complications.

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

• Treatment.

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

• Forecast.

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

The group of papillomaviruses combines more than 100 types of various extracellular agents. Although they cause illnesses that are similar in symptoms - skin growths appear - 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 subsequently resolve without treatment. According to 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 can cause cancer. First of all, types 16 and 18 are dangerous.

• transmission path.

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

• Virus symptoms.

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

• Possible complications.

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

• Treatment.

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

• Forecast.

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

Human papillomavirus in women

Some types of human papillomavirus in women have been shown to be associated with the development of cervical cancer. According to WHO, types 16 and 18 cause 70% of all cases of this cancer.

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

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

Today, vaccines have been developed from HPV 16 and 18, which WHO recommends using at the age of 9-13 years. In the US and some European countries, these vaccinations are included in the vaccination schedule.

Among all inflammations of the liver, 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, the course of the disease and the prognosis.

Hepatitis A and E

Viruses of this group differ from the rest in that they are not capable of causing a chronic disease. Once transferred disease in the vast majority of cases 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 the urine and whitish 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.

• Possible complications.

These inflammations of the liver are dangerous for people with immunodeficiency, as well as during pregnancy. When infected with the virus during pregnancy, hepatitis A is much more difficult to carry, and hepatitis E can cause serious fetal pathologies and, in some cases, death of the mother.

• Treatment.

There is no specific treatment for hepatitis A and E viruses. The main therapy is supportive agents, as well as adherence to a therapeutic diet. A vaccine has been developed for 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 are a major 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 of particular concern. 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 the blood), sexual, vertical. Hepatitis B, sometimes referred to as 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 in a chronic form. A person guesses about the disease only at the critical stages of cirrhosis or liver cancer.

• Possible complications.

Both diseases can turn into chronic infections. Most often this happens in the case of the hepatitis C virus. The chronicity of hepatitis B depends on the age of the patient. So, for example, in infants, the probability of such a course is 80-90%, and for adults - less than 5%. Chronic hepatitis is dangerous with 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 medications are prescribed. However, there is an effective vaccine against the B virus that has been used since 1982. Modern pharmacological developments have made it possible to increase the percentage of the effectiveness of the treatment of 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 severe liver damage up to 20 years after infection, in some cases up to 5-7 years. The risk of developing cirrhosis is 15-30%. Hepatitis B is already dangerous in the acute period if the D virus is also present in the blood. The chronic form of hepatitis B can also cause serious liver damage.

Human Immunodeficiency Virus (HIV)

HIV is now considered one of the most dangerous infections in the world. It is ubiquitous, with approximately 37 million infected people worldwide as of 2014. 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 development of the disease - with acquired immunodeficiency syndrome (AIDS). It is with such a diagnosis that other infections can become more active in a person, a tendency to form malignant tumors appears, 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.

Before the development of AIDS, it is asymptomatic. After that, manifestations of reduced immunity appear, 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 lesions and the development of pathologies.

• Possible 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 and should be lifelong. Thanks to these drugs, HIV can be kept under control, preventing the development of AIDS. The viral load is reduced enough that a person receiving treatment is no longer contagious.

• Forecast.

With timely treatment, HIV-positive people are able to live a full 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 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 during the period of bearing a child. This happens quite rarely, because most of the population is faced with the virus in childhood.

• transmission path.

Through biological fluids - saliva, urine, semen, secretions, as well as 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.

• Possible complications.

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, one that can infect 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 often transmitted from dogs.

• Virus symptoms.

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

• Possible complications.

If symptoms appear, then rabies leads to death.

• Treatment.

Immediately after a bite or possible contact with a rabid animal, vaccination should begin. Treatment of the rabies virus consists of a course of post-exposure prophylaxis (PEP).

• Forecast.

Favorable with timely vaccination.

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

Poliomyelitis is now virtually eradicated by vaccination. The disease has remained endemic in two countries, Pakistan and Afghanistan.

• transmission path.

Fecal-oral.

• Virus symptoms.

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

• Possible complications.

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

• Treatment.

There is no specific treatment. At the same time, vaccination against polio 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.

06.09.2017 17:12

Viral infections are diseases that every person encounters many times throughout life. Basically, these are respiratory viruses that lead to colds, less often - viruses of childhood infections and other pathologies. However, among all, there are such human virusesthat lead to very dangerous, sometimes fatal diseases. There is even a kind of rating of viral infections, the top 10 most dangerous viruses on the planet. What are these infections?

OTHER DANGEROUS VIRUSES

Leads to the formation of the fever of the same name, which occurs in Asia and Africa. It is transmitted from sick to healthy through carriers, gives massive epidemics with a mortality rate of up to 50%. It is difficult to diagnose and treat such a fever. Smallpox is considered to be no less dangerous virus. Enormous forces and means were thrown into the fight against it, thanks to which it was last registered in 1977. But it is important to know that in the laboratories of many countries it is stored as a biological weapon, therefore, it does not lose its relevance.
The rabies virus is a specific infection transmitted through the bites of domestic and wild animals. An infected person can only be saved at an early stage by introducing a special anti-rabies vaccine. In advanced cases, patients die in severe agony. Worldwide, only 3 survivors of the infection have been reported.
The Lassa virus, common in African countries, leads to a special fever, which often ends in death. When the disease affects many internal organs, the nervous system and blood, the disease is highly contagious and causes epidemics.
HIV is the most scandalous and most famous of the deadly viruses. It leads to the gradual destruction of one's own immune system, which gives the AIDS syndrome. For many years, the development of a cure for this infection has been underway, today they have learned to control it and prolong the life of patients, but the complete elimination of the virus from the body has not yet been announced.

In our life there are so many scary stories about evil spirits, ghosts, brownies. But unlike these tales, which still have no evidence, there are really terrible and inexplicable things in the world - mysterious viruses. What is a virus anyway? This is a microscopically small, pathogenic microorganism, which for the most part does not have a cellular structure.

In this article, we will look at the 10 most mysterious viruses on the planet.

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10

black widow virus

Recently, scientists have made a unique discovery. The WO virus, which infects bacteria (bacteriophage), has appropriated the Black Widow spider's venom gene. Previously, it was believed that bacteriophages do not exchange genes with animals, but recently American scientists informed the world that this bacteriophage is able to take pieces of other genes, combining them together, thereby forming a new gene. This is a very unique phenomenon that scientists have recently discovered.

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9

Infertility is the inability of a man and woman to conceive a child with regular sexual activity.

Infertility is divided into two categories - absolute and relative. In women, it can be primary (when pregnancy never occurred) and secondary (pregnancy was, even if it ended in miscarriage or ectopic pregnancy).

Italian scientists conducted research and concluded that one of the causes of infertility may be the HHV-6A virus, one of the herpes viruses. It causes immune responses that prevent the fetus from attaching to the uterine wall. Treatment is with antiviral therapy and injections of the hormone estradiol.

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8

Scientists have discovered an incredibly tenacious microbe in the SIRV2 virus. He is able to survive even in boiling acid. Survives even at a temperature of 175 degrees Celsius. It is also resistant to UV radiation. Scientists have found striking similarities between SIRV2 and bacterial spores from diseases that are difficult to treat, such as anthrax. They intend to study the virus in more detail in order to further use it for gene therapy.

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7

Multicomponent virus

This virus is very unusual, because the usual virus is one, and this one is divided into five parts. To become infected, a cell must be exposed to at least four genes.

The virus was found in the genes of a mosquito, that is, a person needs at least 4 mosquito bites to become infected with the disease. This study was part of a larger project to find out what viruses mosquitoes can carry, but made such an unexpected discovery.

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6

8% of the human genome comes from ancient viruses. Retroviruses target human sperm and eggs in order to further gain a foothold in the DNA of a new person and be transmitted from generation to generation. Despite the fact that millions of years have passed, the virus may reappear. Researchers do not know the exact time of awakening - this can happen during the appearance of new diseases and as a result of the work of a viral cell that is attached to the DNA of our body.

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5

In the summer of 2014, a resident of Bourbon County was bitten by a tick. He went to the hospital complaining of vomiting, rash and high fever. He developed pulmonary and renal insufficiency, on the 11th day he died. A new virus was isolated from his blood and attributed to the Thogotovirus species, among which are the causative agents of meningitis and encephalitis that affect the membranes of the brain. But unlike them, the bourbon virus infects white blood cells. To date, this is the only case of infection with the bourbon virus.

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4

A French research team has discovered a 30,000-year-old virus in the Siberian permafrost! But there is nothing to be afraid of - the virus is not capable of infecting animal or human cells. It struck single-celled amoebas during the Upper Paleolithic or Neolithic. The Siberian virus is wider in diameter than other giants. It has a genome of 600,000 base pairs that can make 500 proteins.

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3

These viruses are responsible for the death of most prokaryotes in the deep ocean, scientists say. As in the entire biosphere of the planet, in the deep ocean, viruses are the most common biological creatures. A partial genetic match has been found between the waters of California and Norway.

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2

Mysterious paralysis

In the United States in 2015, more than a hundred cases of mysterious paralysis in children were recorded. The symptoms started like a common cold. At first, scientists suspected the EV-D68 virus, as it can cause paralysis, but it was found in only 20% of cases. The researchers said that enterovirus D68, and now enterovirus C105, was found in the respiratory tract of children, but was not found in the cerebrospinal fluid. The cause of the mysterious paralysis outbreak is still a mystery.

✰ ✰ ✰

1

This is an acute febrile disease that affects blood vessels and leads to the development of thrombohemorrhagic syndrome. Last year, 129 people died from an unknown disease, but it is not yet clear if they were carriers of the same disease.

Many viruses were found in the blood samples of the dead. Most scientists believe that ticks or mosquitoes carry the disease, but do not exclude that the virus enters the body with bacteria. It is still unknown whether the fever is transmitted from person to person.

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Conclusion

It was an article about the strangest and most mysterious viruses on the planet. Thanks for attention!

Viral diseases infect cells in which there are already violations, which is what the pathogen uses. Modern studies have proven that this happens only with a strong weakening of the immune system, which is no longer able to adequately fight the threat.

Features of viral infections

Types of viral diseases

These pathogens are usually distinguished by a genetic trait:

• DNA - human catarrhal viral diseases, hepatitis B, herpes, papillomatosis, chicken pox, lichen;
• RNA - influenza, hepatitis C, HIV, polio, AIDS.

Viral diseases can also be classified according to the mechanism of influence on the cell:

• cytopathic - the accumulated particles break and kill it;
• immune-mediated - the virus embedded in the genome sleeps, and its antigens come to the surface, putting the cell under attack by the immune system, which considers it an aggressor;
• peaceful - the antigen is not produced, the latent state persists for a long time, replication starts when favorable conditions are created;
• degeneration - the cell mutates into a tumor.

How is the virus transmitted?

The spread of a viral infection is carried out:

1. Airborne. Respiratory viral infections are transmitted by the retraction of mucus particles splattered during a sneeze.
2. Parenterally. In this case, the disease passes from mother to child, during medical manipulations, sex.
3. Through food. Viral diseases come with water or food. Sometimes they stay dormant for a long time, appearing only under external influence.

Why are viral diseases epidemic?

Many viruses spread quickly and massively, which provokes the emergence of epidemics. The reasons for this are as follows:

1. Ease of distribution. Many serious viruses and viral diseases are easily transmitted through saliva droplets inhaled. In this form, the pathogen can maintain activity for a long time, therefore it is able to find several new carriers.
2. reproduction rate. After entering the body, the cells are affected one by one, providing the necessary nutrient medium.
3. Difficulty of elimination. It is not always known how to treat a viral infection, this is due to the lack of knowledge, the possibility of mutations and the difficulties of diagnosing - at the initial stage it is easy to confuse with other problems.

Symptoms of a viral infection

The course of viral diseases may differ depending on their type, but there are common points.

1. Fever. It is accompanied by a rise in temperature to 38 degrees, without it only mild forms of SARS pass. If the temperature is higher, then this indicates a severe course. It does not last longer than 2 weeks.
2. Rash. Viral skin diseases are accompanied by these manifestations. They may look like spots, roseola, and vesicles. It is typical for childhood, in adults rashes are less common.
3. Meningitis. Occurs with an enterovirus and is more common in children.
4. Intoxication- loss of appetite, nausea, headache, weakness and lethargy. These signs of a viral disease are due to toxins released by the pathogen in the course of activity. The strength of the impact depends on the severity of the disease, it is harder for children, adults may not notice it.
5. Diarrhea. Characteristic of rotaviruses, the stool is watery, does not contain blood.

Human viral diseases - list

It is impossible to name the exact number of viruses - they are constantly changing, adding to the extensive list. Viral diseases, the list of which is presented below, are the most famous.

1. Flu and cold. Their signs are: weakness, fever, sore throat. Antiviral drugs are used, when bacteria are attached, antibiotics are additionally prescribed.
2. Rubella. The eyes, respiratory tract, cervical lymph nodes and skin are affected. It spreads by airborne droplets, accompanied by high fever and skin rashes.
3. Piggy. The respiratory tract is affected, in rare cases, the testes are affected in men.
4. Yellow fever. Harms the liver and blood vessels.
5. Measles. Dangerous to children, affects the intestines, respiratory tract and skin.
6. . Often occurs in the background of other problems.
7. Polio. Penetrates into the blood through the intestines and breathing, with brain damage, paralysis occurs.
8. Angina. There are several types, characterized by headache, high fever, severe sore throat and chills.
9. Hepatitis. Any variety causes yellowness of the skin, darkening of the urine and colorless feces, which indicates a violation of several bodily functions.
10. Typhoid. Rare in the modern world, affects the circulatory system, can lead to thrombosis.
11. Syphilis. After the defeat of the genital organs, the pathogen enters the joints and eyes, spreads further. It has no symptoms for a long time, so periodic examinations are important.
12. Encephalitis. The brain is affected, a cure cannot be guaranteed, the risk of death is high.

The most dangerous viruses in the world for humans

The list of viruses that pose the greatest danger to our body:

1. Hantavirus. The causative agent is transmitted from rodents, causes various fevers, mortality in which ranges from 12 to 36%.
2. Flu. This includes the most dangerous viruses known from the news, different strains can cause a pandemic, a severe course affects the elderly and young children more.
3. Marburg. Opened in the second half of the 20th century, it is the cause of hemorrhagic fever. It is transmitted from animals and infected people.
4. . It causes diarrhea, the treatment is simple, but in underdeveloped countries 450 thousand children die from it every year.
5. Ebola. As of 2015, the mortality rate is 42%, it is transmitted by contact with the fluids of an infected person. Signs are: a sharp increase in temperature, weakness, pain in the muscles and throat, rash, diarrhea, vomiting, bleeding is possible.
6. . Mortality is estimated at 50%, intoxication, rash, fever, and lymph node damage are characteristic. Distributed in Asia, Oceania and Africa.
7. Smallpox. Known for a long time, dangerous only to people. Rash, fever, vomiting, and headache are characteristic. The last case of infection occurred in 1977.
8. Rabies. Transmitted from warm-blooded animals, affects the nervous system. After the appearance of symptoms, the success of treatment is almost impossible.
9. Lassa. The pathogen is carried by rats, first discovered in 1969 in Nigeria. The kidneys, nervous system are affected, myocarditis and hemorrhagic syndrome begin. The treatment is difficult, the fever claims up to 5 thousand lives annually.
10. HIV. It is transmitted through contact with the fluids of an infected person. Without treatment, there is a chance to live 9-11 years, its complexity lies in the constant mutation of cell-killing strains.

Fight against viral diseases

The complexity of the fight lies in the constant change of known pathogens, making the usual treatment of viral diseases ineffective. This makes it necessary to search for new drugs, but at the present stage of development of medicine, most measures are developed quickly, before the epidemic threshold is crossed. The following approaches have been adopted:

• etiotropic - prevention of the reproduction of the pathogen;
• surgical;
• immunomodulatory.

Antibiotics for a viral infection

In the course of the disease, there is always a suppression of immunity, sometimes it is necessary to strengthen it to destroy the pathogen. In some cases, with a viral disease, antibiotics are additionally prescribed. This is necessary when a bacterial infection joins, which is killed only in this way. With a pure viral disease, taking these drugs will not only worsen the condition.

Prevention of viral diseases

1. Vaccination- effective against a specific pathogen.
2. Strengthening immunity- Prevention of viral infections in this way involves hardening, proper nutrition, support with plant extracts.
3. Precautionary measures- the exclusion of contacts with sick people, the exclusion of unprotected casual sex.