Dangerous human viral diseases. Which viruses most often infect the human body - an infectious infection. An infectious disease that threatens billions of people

There is a myriad of microorganisms in the world, viruses prevail among them. They can survive in the harshest conditions. Viruses are found in the eternal ice of Antarctica, and in the hot sands of the Sahara, and even in the cold vacuum of space. Although not all of them are dangerous, more than 80% of all human diseases are caused by viruses.

Back in the 40s of the last century, mankind knew about 40 diseases provoked by them. Today this figure is more than 500, not counting the fact that every year new species are discovered. People have learned how to fight viruses, but knowledge is not always enough - more than 10 of their species remain the most dangerous for humanity. Viruses are the causative agents of dangerous human diseases. Let's take a look at the main ones.

Hantaviruses

The most dangerous type of virus is hantavirus. Contact with small rodents or their waste products is likely to become infected. They can provoke many diseases, the most dangerous of which are hemorrhagic fever and hantavirus syndrome. The first disease kills every tenth, the probability of death after the second is 36%. The largest outbreak occurred during the Korean War. Then more than 3,000 soldiers from different sides of the confrontation felt its effect. There is a high probability that the hantavirus caused the extinction of the Aztec civilization 600 years ago.

Ebola virus

What other dangerous viruses exist on Earth? The epidemic created panic in the global community just a year ago. The virus was discovered in 1976 during an epidemic in the Congo. It got its name in honor of the pool where the outbreak happened. Ebola has many symptoms, making it difficult to diagnose. The most common of them include: fever, general weakness, vomiting, impaired liver and kidney function, sore throat. In some cases, internal and external bleeding is observed. In 2015, this virus took the lives of more than 12 thousand people.

Why is the flu virus dangerous?

Of course, no one would argue that a dangerous virus is a common flu. More than 10% of the world's population suffers from it every year, which makes it one of the most common and unforeseen.

The main danger to people is not the virus itself, but the complications it can cause (kidney disease, pulmonary and brain edema, heart failure). Of the 600 thousand people who died last year from influenza, only 30% of deaths were directly caused by the virus, the death of the rest is the result of complications.

Mutations are another danger of the flu virus. Due to the constant use of antibiotics, the disease gets worse every year. Chicken and swine flu, the epidemics of which have broken out over the past 10 years, is another confirmation of this. In the worst case scenario, in a few decades, drugs that can fight the flu will pose an extreme danger to humans.

Rotavirus

The most dangerous type of virus for children is rotavirus. Although the cure for it works quite effectively, about half a million babies die from this disease every year. This disease causes acute diarrhea, the body quickly dehydrates and death occurs. Most of those affected live in underdeveloped countries where vaccine against the virus is difficult to obtain.

Deadly Marburg

The Marburg virus was first detected in the city of the same name in Germany in the late 60s of the last century. It is one of the ten deadly viruses that can be transmitted from animals.

About 30% of diseases with this virus are fatal. In the early stages of this disease, a person is tormented by fever, nausea, and muscle pain. With a more severe course - jaundice, pancreatitis, liver failure. The disease is transmitted not only by humans, but also by rodents, as well as some species of monkeys.

Hepatitis in action

What other dangerous viruses are known? There are more than 100 types of them that affect the human liver. The most dangerous of them are hepatitis B and C. It is not for nothing that this virus is nicknamed the "gentle killer", because it can be in the human body for many years without causing tangible symptoms.

Hepatitis most often leads to the death of liver cells, that is, to cirrhosis. It is almost impossible to cure the pathology caused by strains B and C of this virus. By the time hepatitis is detected in the human body, the disease, as a rule, is already in a chronic form.

The discoverer of this disease was the Russian biologist Botkin. The strain of hepatitis he found is now called "A", and the disease itself is treatable.

Smallpox virus

Smallpox is one of the oldest diseases known to mankind. It only affects humans, causing them chills, dizziness, headaches, and pain in the lower back. The characteristic signs of smallpox are the appearance of a purulent rash on the body. In the past century alone, smallpox has claimed the lives of about half a billion people. Colossal financial resources (about $ 300 million) were thrown to fight this disease. Nevertheless, virologists have achieved success: the last known case of smallpox was recorded forty years ago.

Deadly rabies virus

The rabies virus is the first of this ranking, leading to death in 100% of cases. You can become infected with rabies after being bitten by a sick animal. The disease is asymptomatic until the time when it is no longer possible to save a person.

The rabies virus causes severe damage to the nervous system. In the last stages of the disease, a person becomes violent, experiences a constant feeling of fear, suffers from insomnia. A few days before death occurs blindness and paralysis.

In the entire history of medicine, only 3 people have been saved from rabies.

Lassa virus

What other dangerous diseases are known to be caused by this virus - one of the most dangerous diseases in West Africa. It affects the human nervous system, kidneys, lungs, and can cause myocarditis. During the entire period of the illness, the body temperature does not drop below 39-40 degrees. Many painful, purulent ulcers appear on the body.

Lassa virus is carried by small rodents. The disease is transmitted by contact. Every year, about 500 thousand people are infected, of which 5-10 thousand die. In severe Lassa fever, mortality can be as high as 50%.

Acquired Immunodeficiency Syndrome

The most dangerous type of virus is HIV. He is considered the most dangerous of those that are known to man at this time.

Experts have found that the first case of transmission of this virus from primate to humans happened in 1926. The first death was recorded in 1959. In the 60s of the last century, AIDS symptoms were found in American prostitutes, but then they did not attach much importance to this. HIV was considered simply a complex form of pneumonia.

HIV was recognized as a separate disease only in 1981, after the outbreak of an epidemic among homosexuals. Within 4 years, scientists have figured out the ways of transmission of this disease: blood and semen. The real AIDS epidemic in the world began 20 years ago. HIV is rightfully called the plague of the 20th century.

This disease primarily affects the immune system. As a result, AIDS itself is not fatal. But an HIV-infected person who simply lacks immunity can die from a simple cold.

All attempts to invent so far have been unsuccessful.

Why is the papilloma virus dangerous?

About 70% of people are carriers of the papillomavirus, most of them are women. Papilloma is transmitted sexually. Of more than 100 types of papillomavirus, about 40 lead to various diseases. As a rule, the virus infects the human genitals. Its external manifestation is the appearance of growths (papillomas) on the skin.

The incubation period of the virus after entering the body can last from several weeks to several years. In 90% of cases, the human body itself will get rid of foreign micro-objects. The virus is dangerous only for a weakened immune system. Therefore, papilloma often manifests itself during other diseases, such as influenza.

The most serious consequence of papilloma can be cervical cancer in women. 14 known strains of this virus are highly oncogenic.

Is bovine leukemia virus dangerous for humans?

Viruses can infect not only humans, but also animals. Since a person eats animal products, the question of the danger of such pathogens to humans is increasingly raised.

The leukemia virus is in the first place in terms of damage. It infects the blood of cows, sheep, goats and provokes serious illness, and in some cases death.

Studies show that more than 70% of people have antibodies in their blood that can fight the bovine leukemia virus. However, this does not exclude the possibility of human infection with this virus. The likelihood that bovine leukemia can lead to blood cancer in humans is very small, but there is the possibility of other negative consequences. The leukemia virus can attach to human cells, causing mutations. In the future, this could create a new strain of it, which will be equally dangerous to both animals and humans.

While viruses can be beneficial to humans, this does not override their harm. More people died from them than died in all the wars of the world at all times. This article has listed the most dangerous viruses in the world. We hope you find this information useful. Be healthy!

Hantaviruses.
Hantaviruses are a genus of viruses transmitted to humans through contact with rodents or their metabolic products. Hantaviruses cause various diseases related to such groups of diseases as “hemorrhagic fever with renal syndrome” (mortality rate is 12% on average) and “hantavirus cardiopulmonary syndrome” (mortality rate up to 36%). The first major outbreak of the disease caused by hantaviruses, known as Korean Hemorrhagic Fever, occurred during the Korean War (1950-1953). Then more than 3,000 American and Korean soldiers felt the impact of a then unknown virus that caused internal bleeding and impaired kidney function. Interestingly, it is this virus that is considered the likely cause of the outbreak in the 16th century, which destroyed the Aztec people.

Influenza virus.
Influenza virus is a virus that causes acute respiratory infections in humans. Currently, there are more than 2 thousand variants of it, classified into three serotypes A, B, C. A group of the virus from serotype A divided into strains (H1N1, H2N2, H3N2, etc.) is the most dangerous for humans and can lead to epidemics and pandemics. Every year in the world from seasonal flu epidemics die from 250 to 500 thousand people (most of them are children under 2 years old and elderly people over 65 years old).

Marburg virus.
The Marburg virus is a dangerous human virus, first described in 1967 during small outbreaks in the German cities of Marburg and Frankfurt. In humans, it causes Marburg hemorrhagic fever (mortality 23-50%), which is transmitted through blood, feces, saliva and vomit. The natural reservoir for this virus is sick people, probably rodents and some species of monkeys. Early symptoms include fever, headache, and muscle pain. In the later, jaundice, pancreatitis, weight loss, delirium and neuropsychiatric symptoms, bleeding, hypovolemic shock, and multiple organ failure, most commonly the liver. Marburg fever is one of the ten deadly animal-borne diseases.

Rotavirus.
The sixth most dangerous human virus is Rotavirus, a group of viruses that are the most common cause of acute diarrhea in infants and young children. It is transmitted by the fecal-oral route. The disease is usually easily treatable, but more than 450,000 children under the age of five die each year worldwide, most of whom live in underdeveloped countries.

Ebola virus.
The Ebola virus is a genus of viruses that causes Ebola haemorrhagic fever. It was first discovered in 1976 during an outbreak in the Ebola River Basin (hence the name of the virus) in Zaire, DR Congo. It is transmitted by direct contact with blood, secretions, other fluids and organs of an infected person. Ebola is characterized by a sudden increase in body temperature, severe general weakness, muscle and headaches, and sore throat. It is often accompanied by vomiting, diarrhea, rash, impaired renal and liver function, and in some cases, internal and external bleeding. According to the US Centers for Disease Control, as of 2015, 30,939 people were infected with Ebola, of whom 12,910 (42%) died.

Dengue virus.
Dengue virus is one of the most dangerous viruses for humans, causing dengue fever in severe cases, with a death rate of about 50%. The disease is characterized by fever, intoxication, myalgia, arthralgia, rash, and swollen lymph nodes. It occurs mainly in the countries of South and Southeast Asia, Africa, Oceania and the Caribbean, where about 50 million people are infected annually. The carriers of the virus are sick people, monkeys, mosquitoes and bats.

Smallpox virus.
The smallpox virus is a complex virus, the causative agent of the highly contagious disease of the same name that affects only humans. This is one of the oldest diseases, the symptoms of which are chills, pain in the sacrum and lower back, a rapid increase in body temperature, dizziness, headache, vomiting. On the second day, a rash appears, which eventually turns into purulent blisters. In the 20th century, this virus claimed the lives of 300-500 million people. The smallpox campaign spent about US $ 298 million between 1967 and 1979 (the equivalent of US $ 1.2 billion in 2010). Fortunately, the last known case of infection was reported on October 26, 1977 in the Somali city of Marka.

Rabies virus.
The rabies virus is a dangerous virus that causes rabies in humans and warm-blooded animals, in which a specific damage to the central nervous system occurs. This disease is transmitted through saliva by the bite of an infected animal. It is accompanied by an increase in temperature to 37.2-37.3, poor sleep, patients become aggressive, violent, hallucinations, delirium, a feeling of fear appear, paralysis of the eye muscles, lower extremities, paralytic respiratory disorders and death soon occur. The first signs of the disease appear late, when destructive processes have already taken place in the brain (edema, hemorrhage, degradation of nerve cells), which makes treatment almost impossible. To date, only three cases of human recovery have been recorded without the use of vaccination, all the rest ended in death.

Lassa virus.
Lassa virus is a deadly virus that causes Lassa fever in humans and primates. The disease was first discovered in 1969 in the Nigerian city of Lassa. It is characterized by a severe course, damage to the respiratory system, kidneys, central nervous system, myocarditis and hemorrhagic syndrome. It occurs mainly in West African countries, especially in Sierra Leone, the Republic of Guinea, Nigeria and Liberia, where the annual incidence ranges from 300,000 to 500,000 cases, of which 5,000 lead to patient death. The natural reservoir of Lassa fever is the multi-nipple rat.

AIDS virus.
Human Immunodeficiency Virus (HIV) is the most dangerous human virus, the causative agent of HIV / AIDS, which is transmitted through direct contact of the mucous membranes or blood with bodily fluid of the patient. In the course of HIV infection, all new strains (varieties) of the virus are formed in the same person, which are mutants, completely different in reproduction speed, capable of initiating and killing certain types of cells. Without medical intervention, the average life expectancy of a person infected with the immunodeficiency virus is 9-11 years. According to data for 2011, 60 million people in the world fell ill with HIV infection, of which 25 million died, and 35 million continue to live with the virus.

Acellular infectious agent. It has a genome (DNA or RNA), but lacks its own synthesizing apparatus. It is capable of reproduction only when it gets into the cells of more highly organized creatures. Reproducing, 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 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 special complications, with a noticeable lesion of the salivary and parotid glands. However, the virus in men is 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 vaccination is the best protection against disease. 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 of its types 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 to identify a dangerous virus in women of different ages in time. It should be said that a factor such as smoking affects the activity of the papilloma virus - it contributes to the transformation 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. At the same time, the severity 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. 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 injury decreases significantly, and most often pathologies manifest themselves only as deafness. In the early stages, the virus can cause bone damage, deformity, blindness, heart defects, and brain damage in the fetus.

• Herpesvirus 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, the herpes simplex virus type II 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 the 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 be vaccinated 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 "often 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, - the well-known pediatrician Yevgeny Komarovsky believes.

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.

The 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 through 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 the 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 along 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, they are usually divided into DNA-containing and RNA-containing (Baltimore classification).

• DNA viruses.

Their replication (reproduction) occurs in the cell nucleus, and the process of the formation of 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 capable of making 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 was 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 - with them scientists associate 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 a capsomere. While in the 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 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 types. It is 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 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.

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. Such infections are often seasonal in nature - infection with the virus occurs in warm weather, in summer.

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

Viruses transmitted in this way are dangerous during blood transfusions, surgical interventions 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 insect and tick bites.

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 intercourse.

The route of transmission is also typical for 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 disease. 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 the virus (illness, vaccination).

Some infections, such as measles, rubella, poliomyelitis, can cause epidemics among children and hardly affect the adult population. This is precisely due to the presence of acquired immunity. Moreover, if with the help of vaccination "collective immunity" is provided, such viruses will not be able to cause epidemics in children's collectives.

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 vaccination and revaccination, 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 in 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, which is life-long and incurable. However, the disease rarely causes serious inconvenience, manifesting itself only occasionally with ulcers on the lips, genitals and mucous membranes.

Many types of human papillomavirus have 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 diseases. 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. ARVI 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 is distinguished by special symptoms, 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. Human viruses that cause respiratory diseases 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 safe enough, 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 the WHO, leads to the development of a chronic disease ending in liver cancer or cirrhosis. 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 tests 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 course of 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 decoded 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. End of the disease, or exacerbation of the 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 turn into a chronic form, and what harm it can do to 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 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 go into the chronic stage include:

• SARS, including influenza
• Rubella
• Mumps
• 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 a 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, and also 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 are 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 a chronic form, 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 often, 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 a high oncological 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 it 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 using 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 application 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.

Moreover, some viruses in one way or another are able to resist the defense system and not elicit 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. Among these infections are 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.

Mostly 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 does not act on the virus in any way, 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, 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 earlier. There are 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 memorize 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 former can be called broad-spectrum drugs, but 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 rather 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 a viral illness, but cannot completely eliminate the virus.

• Flu.

According to the WHO recommendation, inhibitors of influenza neuraminidase (Oseltamivir and Zanamivir) are now 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 - a 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.

Precautions

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 before symptoms appear, this is how the whole community can be prevented from getting the virus.

During 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.
• Cosmetic procedures 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 at risk of being infected 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 precautions do not provide a 100% protection against viruses. To date, the most reasonable way to prevent viral infections is vaccination.

Pharmacists have developed vaccines that are effective against over 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 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 through mass immunization that it has been possible to reduce the number of cases of infection with the virus by 99%. As of 2016, poliomyelitis 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 adenovirus that is a common cause of the development 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.

• Symptoms of the virus.

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 laryngeal mucosa, as well as rhinitis. In case of eye damage - redness of the mucous membranes, itching, pain.

• Possible complications.

They rarely appear, a bacterial infection may join, which will cause pneumonia, otitis media, 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 respiratory tract 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. At the same time, some strains are capable of leading to quite serious diseases, often fatal. Every year, even in the absence of serious pandemics, according to the 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.

• Symptoms of the virus.

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.

• 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 an 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, the introduction of interferons is possible.

• 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 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 droplets, while the virus is able to move with a stream of air over distances of up to 20 m.

• Symptoms of the virus.

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.

• Possible 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

Herpes simplex virus is of two types. 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 into 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 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.

• Symptoms of the virus.

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.

• Possible 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% is 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).

• Symptoms of the virus.

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, some types (1, 2, 4) are characterized by lesions of the feet, 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.

• Possible 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. For people with severe symptoms, surgical removal of warts, warts, and papillomas is recommended.

• Forecast.

Generally favorable. Even HPV types with high cancer risk can be controlled. The key to 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 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 to regenerate a neoplasm, if a woman has no problems with immunity. For HIV-infected people, 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 encouraged 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 noticeable and have a high cancer risk.

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. These types of hepatitis viruses are distinguished - 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 overwhelming 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.

• Symptoms of the virus.

Hepatitis A and E is manifested by nausea, vomiting, pain in the liver, fever, and 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.

• Possible complications.

These liver inflammations are dangerous for people with immunodeficiency and 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.

• Possible 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 to 90%. Direct-acting antiviral drugs are now 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 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, a tendency to form malignant tumors appears, and 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, Epstein-Barr virus, cytomegalovirus. Other viruses (measles, rubella, influenza,) lead to serious injuries 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 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, 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 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.

• Symptoms of the virus.

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.

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.

• Symptoms of the virus.

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, light and hydrophobia, hallucinations, a sense of fear, aggression appear. The disease ends with muscle paralysis and breathing disorders.

• Possible 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, favorable.

Poliomyelitis mainly affects children under 5 years of age. In most cases, it does not cause serious health effects, but 1 in 200 people infected with the virus will cause 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.

• Symptoms of the virus.

With the 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.

• Possible 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 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.

Let's analyze viral infectionsto understand what they are, how they develop in the bodies of infected people, what the symptoms are and how to treat them.

What is a viral infection

Viral infection is a disease caused by infectious microorganisms, viruses that enter the cells of a living organism and use its mechanisms to multiply.

In order to perform its vital functions, it needs to colonize the host organism and gain access to biochemical replication mechanisms. Therefore, viruses infect the cells of living organisms, capture them and colonize them. Once inside the cell, the virus embeds its genetic code into DNA or RNA, thereby forcing the host cell to reproduce the virus.

As a rule, as a result of such infection, the cell loses its natural functions and dies (apoptosis), but manages to replicate new viruses that infect other cells. Thus, a general infection of the whole organism develops.

There are categories of viral infections that, instead of killing the host cell, alter its characteristics and functions. And it may happen that this will disrupt the natural process of cell division and it will turn into a cancer cell.

In other cases, the virus after infection of the cell can go into a "dormant" state. And only after some time, under the influence of some event that upsets the balance achieved, the virus awakens. It begins to multiply again and a relapse of the disease develops.

How does the virus get infected?

Infection occurs when a virus gets the opportunity to penetrate the body, overcoming its natural defensive barriers. Once in the body, it multiplies either at the site of penetration, or, with the help of blood and / or lymph, gets to the target organ.

Obviously, the way in which viruses are transmitted is important.

The most common are:

• Fecal-oral intake;
• Ingestion;
• Insect bites and therefore the cutaneous pathway;
• Through microscopic damage to the mucous membrane of the genital apparatus of men and women;
• Through direct contact with blood (using used syringes or toilet items);
• Vertical transmission from mother to fetus through the placenta.

How a viral infection develops

Development of a viral infection depends on various parameters, in particular:

• From the characteristics of the virus... Those. the ease with which it passes from one host to another, on how easily it is possible to overcome the protection of the new host, on how successfully the organism resists it, and on how much damage it can create.
• From the characteristics of the host's immune system... In the human body, in addition to natural physical barriers (skin, mucous membranes, gastric juice, etc.), there is an immune system. Its task is to organize internal defense and destroy potentially dangerous substances such as viruses.
• From the conditions of the environment in which the owner lives... There are certain factors that obviously contribute to the spread and development of the infection. An example of this is the natural and climatic conditions.

After infection, the immune system develops a reaction, which can lead to three outcomes:

• White blood cells, in particular lymphocytes, identify the enemy, attack it and, if possible, destroy it along with the infected cells.
• The virus manages to overcome the body's defenses and the infection spreads.
• A state of equilibrium is achieved between the virus and the body, resulting in chronic infection.

If the immune system manages to overcome the infection, then the lymphocytes retain the memory of the offender. Thus, if a pathogen in the future tries to invade the body again, then, based on previous experience, the immune system will quickly eliminate the threat.

It is important to note that the vaccine works on this principle. It includes inactivated viruses or parts of them, and therefore is not able to cause real infection, but is useful for "training" the immune system.

The most common viral infections

As a rule, each virus infects a specific type of cells, for example, cold viruses enter the cells of the respiratory tract, rabies and encephalitis viruses infect cells of the central nervous system. Below you will find the most common viral infections.

Viral Respiratory Tract Infections

They are, of course, the most common and concern the nose and nasopharynx, throat, upper and lower respiratory tract.

Viruses that most commonly affect the breathing apparatus:

• Rhinoviruses are responsible for the common cold that affects the epithelium of the nose, throat and upper respiratory tract. It is transmitted through nasal discharge and enters the body through the mouth, nose, or eyes. Less commonly, colds spread through the air.
• Orthomyxovirus, in its various variants, is responsible for influenza. There are two types of influenza viruses, A and B, and each has many different strains. The influenza virus strain mutates constantly, each year bringing in a new virus that is different from the previous one. Influenza attacks the upper and lower respiratory tract, lungs, and spreads by airborne droplets when coughing and sneezing.
• Adenoviruses pharyngitis and sore throat respond.

Viral infections upper respiratory tract infections are most common in adults, while viral infections of the lower respiratory tract are more common in newborns and children, as well as laryngitis, which is common in newborns, tracheitis, bronchitis and pneumonia.

Viral skin infections

There are many viral diseases that affect the skin, many of them mainly affect children, for example, measles, chickenpox, rubella, mumps, and warts. In this area, herpes viruses, to which the varicella-zoster virus belongs.

There are 8 different types known, numbered 1 to 8. Infections with type 2 of the herpes virus are especially common: the Epstein-Barr virus, which causes monoculeosis, and cytomegalovirus. Herpes simplex virus type 8 causes cancer in immunocompromised patients with AIDS.

Some of the viral infections described are very dangerous during pregnancy (rubella and cytomegalovirus) because they are more likely to cause fetal malformations and miscarriages.

All herpes viruses lead to the development of chronic infections. Viruses remain latent in the host. But in some cases they can “wake up” and cause relapses. A typical example is the herpes virus, which causes chickenpox. In a latent form, the virus hides in the nerve ganglia of the spine in the immediate vicinity of the spinal cord and sometimes wakes up, causing inflammation of the nerve endings with severe pain, which is accompanied by the formation of a skin rash.

Viral infections of the gastrointestinal tract

Gastrointestinal tract infections cause rotaviruses and hepatitis virus, noroviruses... Rotaviruses are transmitted through feces and more often affect children and adolescents, manifesting characteristic gastrointestinal symptoms: nausea, vomiting, abdominal pain and diarrhea. Hepatitis viruses are transmitted through the consumption of contaminated food. Noroviruses are transmitted by the fecal-oral route, but can also enter the respiratory tract and cause flu-like syndromes with lesions of the gastrointestinal tract, and therefore diarrhea and vomiting.

Genital Viral Infections

The virus that affects the reproductive organs of men and women includes the herpes virus, human papillomavirus, and human immunodeficiency virus.

The infamous HIV, which causes acquired immunodeficiency syndrome, deserves special mention, which is reflected in a sharp decrease in the effectiveness of the immune system.

Viral infections and cancers

Some types of viruses, as already mentioned, do not kill the host cell, but only change its DNA. All this leads to the fact that in the future the replication process may be disrupted and a tumor may form.

The main types of viruses that can cause cancer are:

• Papilloma virus... May lead to the development of cervical cancer.
• HBV and HCV virus... May cause liver cancer.
• Herpes virus 8... It is the cause of the development of Kaposi's sarcoma (skin cancer, very rare) in AIDS patients.
• Epstein-Barr virus (Infectious mononucleosis). May cause Burkitt's lymphoma.

How viral infections are treated

Medicines used to fight viral infections are simply called antiviral drugs.

They work by blocking the replication process of the virus responsible for the infection. But, as the virus spreads through the cells of the body, the scope of action of these drugs is limited, since the structures in which they are effective are numerically limited.

In addition, they are highly toxic to body cells. All this leads to the fact that antiviral drugs are very difficult to use. More confusing is the ability of viruses to adapt to drugs.

The most commonly used are the following antiviral drugs:

• Acyclovir against herpes;
• Cidofovir against cytomegalovirus;
• Interferon alpha against hepatitis B and C
• Amantadine against influenza type A
• Zanamivir for influenza A and B.

Therefore, the best treatment of viral infections what remains is prevention, which is based on the use of the vaccine. But even this weapon is difficult to use, given the rapidity of mutation of some viruses. A typical example is the influenza virus, which mutates so quickly that an entirely new strain flares up every year, forcing the introduction of a new type of vaccine to combat it.

It is absolutely useless to take antibiotics for diseases caused by viruses. Antibiotics target bacteria. They should be used only in special cases and as directed by a doctor if he believes that a secondary bacterial infection has joined the viral infection.

Modern people are used to a wide variety of medicines in pharmacies. If necessary, each person takes means to maintain health, strengthen immunity. Bacteria and viruses constantly live around people. Why are viruses dangerous? What consequences do they lead to? This article can answer these questions.

Consequences of viral diseases

Viral infections can cause great harm to the human body. As a rule, a person is emaciated, and his state of health is far from the best. Many medicines for viral infections are sold on the Internet, including the capsid antigen of the Epstein-Barr virus, which is presented on this site.

If such infections are treated on time, seek help from specialists and take special means, then viruses will not have time to greatly harm a person, he will be able to get rid of them.

However, if a person does not treat a viral disease, it becomes chronic, which can affect the work of human organs, the musculoskeletal system and the nervous system. Viruses make the body weaker. A person often feels weak and tired. Viral infections must be treated without fail. At the first symptoms, you need to see a doctor.

Some infections are transmitted by airborne droplets. Experts advise avoiding places where there are many people. Be sure to wash your hands before eating. Vegetables and fruits should also be washed before eating. Many infections are spread precisely because a person did not wash their hands in time. This must be done.

Thus, viral infections are called dangerous diseases that are treated with the help of special drugs. Only a specialist can prescribe the correct, suitable drug. To buy medicine on your own, not to see a doctor is the wrong way of treatment. In case of ailments, you should contact a specialist. As you can see, viruses are very dangerous for humans, but adherence to basic hygienic rules will help to circumvent these dangers.