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Viral diseases - symptoms, diagnosis and treatment. Viral diseases - a list of common ailments and the most dangerous viruses Names of viruses in biology list

Viruses are non-cellular infectious agents that have a genome (DNA and RNA), but are not gifted with a synthesizing apparatus. To reproduce, these microorganisms need cells of more highly organized organisms. Once in the cells, they begin to multiply, causing the development of various diseases. Each virus has a specific mechanism of action on its carrier. Sometimes a person does not even suspect that they are a virus carrier, since the virus does not harm health, this condition is known as latency, such as herpes.

To prevent viral diseases, it is important to maintain a healthy lifestyle, strengthening the body's defenses.

Origin and structure

There are several hypotheses for the origin of viruses. Science offers a version of the origin of viruses from fragments of RNA and DNA that were released from a large organism.

Coevolution suggests that viruses appeared simultaneously with living cells as a result of the construction of complex sets of nucleic acids and proteins.

Questions about how it reproduces and is transmitted are studied by a special section of microbiology - virology.

Each viral particle has genetic information (RNA or DNA) and a protein membrane (capsid) that acts as a defense.

Viruses come in a variety of shapes, ranging from simple helical to icosahedral. The standard value is approximately 1/100 of the size of an average bacterium. However, most viruses are very small, making them difficult to examine under a microscope.

Is living matter a virus?

There are two definitions of life forms of viruses. According to the first, extracellular agents are a collection of organic molecules. The second definition states that viruses are a special form of life. It is impossible to answer the question of what viruses exist, specifically and definitively, since biology assumes the constant emergence of new species. They are similar to living cells in that they have a special set of genes and evolve according to the way the natural set. They require a host cell to exist. The lack of their own metabolism makes it impossible to reproduce without outside help.

Modern science has developed a version according to which certain bacteriophages have their own immunity, capable of adapting. This is proof that viruses are a form of life.

Viral diseases - what is it?

Viruses of the plant world

If you ask yourself what viruses are, then, in addition to the human body, you can distinguish a special type of viruses that infect plants. They are not dangerous to humans or animals, since they can only reproduce in plant cells.

Artificial viruses

Artificial viruses are created to produce vaccines against infections. The list of artificially created viruses in the arsenal of medicine is not fully known. However, it is safe to say that the creation of an artificial virus can have a lot of consequences.

Such a virus is obtained by introducing into the cell an artificial gene that carries the information necessary for the formation of new types.

Viruses that infect the human body

What viruses are on the list of extracellular agents dangerous to humans and causing irreversible changes? Here is an aspect of the study of modern science.

The simplest viral disease is the common cold. But against the background of a weakened immune system, viruses can cause quite serious pathologies. Each pathogenic microorganism affects the organism of its host in a certain way. Some viruses can live in the human body for years and do no harm (latentness).

Certain latent species are even beneficial to humans, as their presence generates an immune response against bacterial pathogens. Some infections are chronic or lifelong, which is purely individual and due to the protective ability of the virus carrier.

Spread of viruses

Broadcast viral infections in humans it is possible from person to person or from mother to baby. The rate of transmission or epidemiological status depends on the population density of the area, the weather and season, and the quality of medicine. It is possible to prevent the spread of viral pathologies if it is timely clarified which virus is currently detected in most patients, and appropriate preventive measures are taken.

Kinds

Viral diseases manifest themselves in completely different ways, which is associated with the type of extracellular agent that caused the disease, with the place of localization, with the rate of development of the pathology. Human viruses are classified as lethal and indolent. The latter are dangerous because the symptoms are unexpressed or weak, and it is not possible to quickly detect the problem. During this time, the pathogenic organism can multiply and cause serious complications.

Below is a list of the main types of human viruses. It allows you to clarify which viruses are there and which pathogenic microorganisms cause diseases that are dangerous to health:

Orthomyxoviruses. This includes all types of influenza viruses. To find out which influenza virus caused the pathological condition, special tests will help.
adenoviruses and rhinoviruses. They affect the respiratory system, cause SARS. Symptoms of the disease are similar to flu, can cause such serious complications as pneumonia, bronchitis.
Herpesviruses. Activated against the background of reduced immunity.
Meningitis. Pathology is caused by meningococci. The mucous membrane of the brain is affected, the nutrient substrate for the pathogenic organism is the cerebrospinal fluid.
Encephalitis. It has a negative effect on the membrane of the brain, causing irreversible changes in the central nervous system.
Parvovirus. The diseases caused by this virus are very dangerous. The patient has convulsions, inflammation of the spinal cord, paralysis.
Picornaviruses. Cause hepatitis.
Orthomyxoviruses. Provoke mumps, measles, parainfluenza.
Rotavirus. The extracellular agent causes enteritis, intestinal flu, gastroenteritis.
rhabdoviruses. They are causative agents of rabies.
Papoviruses. Cause papillomatosis in humans.

Retroviruses. They are the causative agents of HIV, and after AIDS.

life-threatening viruses

Some viral diseases are quite rare, but they pose a serious danger to human life:

Tularemia. The disease is caused by the Francisellatularensis bacillus. The clinical picture of the pathology resembles the plague. It enters the body by airborne droplets or by a mosquito bite. Transmitted from person to person.
Cholera. The disease is fixed very rarely. Vibrio cholerae virus enters the body through the use of contaminated water, contaminated food.
Creutzfeldt-Jakob disease. In most cases, the patient has a lethal outcome. It is transmitted through contaminated animal meat. The causative agent is a prion - a special protein that destroys cells. Manifested by a mental disorder, severe irritation, dementia.

It is possible to determine which type of virus caused the disease by conducting laboratory tests. An important argument is the epidemic state of the region. It is also important to find out which virus is currently circulating.

Signs of viral infections and possible complications

The main part of the viruses provokes the occurrence of acute respiratory diseases. The following manifestations of SARS are distinguished:

development of rhinitis, cough with clear mucus;
an increase in temperature to 37.5 degrees or fever;
feeling of weakness, headaches, decreased appetite, muscle pain.

Late treatment can cause serious complications:

adenovirus can cause inflammation of the pancreas, which leads to the development of diabetes;
beta-hemolytic streptococcus, which is the causative agent of tonsillitis and other types of inflammatory diseases, with reduced immunity can provoke diseases of the heart, joints, epidermis;
influenza and SARS are often complicated by pneumonia in children, elderly patients, pregnant women.

Viral pathologies can also cause other serious complications - sinusitis, joint damage, heart pathology, chronic fatigue syndrome.

Diagnostics

Experts determine a viral infection by common symptoms, based on which virus is currently circulating. Virological studies are used to determine the type of virus. Modern medicine widely uses methods of immunodiagnostics, including immunoindication, serodiagnostics. What to pass the specialist decides on the basis of visual inspection and collected history.

Appoint:

enzyme immunoassay;
radioisotope immunoassay;
study of hemagglutination inhibition response;
immunofluorescence reaction.

Treatment of viral diseases

The course of treatment is chosen depending on the pathogen, specifying which types of viruses caused the pathology.

For the treatment of viral diseases are used:

Drugs that stimulate the immune system.
Medicines that destroy a specific type of virus. The diagnosis of a viral infection is necessary, since it is important to clarify which virus responds best to the selected drug, which makes it possible to make therapeutic therapy more targeted.
Medicines that increase the sensitivity of cells to interferon.

For the treatment of common viral diseases, apply:

"Acyclovir". Assign for herpes, it eliminates the pathology completely.
Relezan, Ingavirin, Tamiflu. Assign for different types of influenza.
Interferons together with Ribavirin are used to treat hepatitis B. A new generation drug, Simeprevir, is used to treat hepatitis C.

Prevention

Preventive measures are selected depending on the type of virus.

Preventive measures are divided into two main areas:

Specific. They are carried out with the aim of developing specific immunity in humans through vaccination.
Nonspecific. Actions should be aimed at strengthening the body's defense system, through the provision of small physical exertion, a properly composed diet and personal hygiene.

Viruses are living organisms that are almost impossible to avoid. To prevent serious viral pathologies, it is necessary to vaccinate according to the schedule, lead a healthy lifestyle, and organize a balanced diet.

Methods of dealing with viral diseases.

Diagnosis of viral diseases.

Methods of transmission of viral diseases.

1. When propagating plants vaccination, on the root. It is important that the queen cells are free from viruses.

2. contact infection. As a result of leaf contact, for example, through hair breakage (trichomes) when rubbing the leaves, through processing tools, garden tools, workers' clothes, especially when pinching, cutting flowers. (tulip variegation virus).

3. Transmission by vectors. The most common way. Viruses can be transmitted by insects, nematodes, fungi. Most carriers of gray aphids, cicadas, thrips, whiteflies. (potato virus, cucumber, pea, beet mosaic virus)

Symptoms of viral diseases can vary greatly depending on a wide variety of conditions, so the diagnosis of viral diseases can be difficult.

1. visual inspection. The fastest but least accurate method.

2. Serological method. If a virus is introduced into the blood of an animal, then specific proteins are formed in the blood serum - antibodies to this virus, transferring it to a harmless state. To diagnose a disease, a drop of the juice of an affected plant is mixed with a drop of diagnostic serum from the blood of an animal previously treated with a known virus. If the juice contains this virus, then as a result of the reaction of the virus and antibodies in the mixture, a flocculent precipitate is formed, the intensity of which can be used to judge the relative amount of virus in the plant sap.

3. indicator method. Based on infection of the indicator plant with the juice of the test plant. Indicators respond with certain clear symptoms to infection with this virus. This is a more sensitive, but also more time-consuming method.

4. Inclusion analysis method. With a razor blade, a section of the epidermis with leaf hairs is cut off and under a microscope they look for viral inclusions in the cells of the hairs.

1. Destruction of diseased plants.

2. Use only healthy planting material.

3. Fight against insects - carriers of viruses.

4. Improvement of plants by meristem culture.

5. Disinfection of planting material by thermotherapy.

On the carnation garden About 9 viral diseases were noted:

Bushiness virus. There is a sharp shortening of the internodes, dormant buds begin to grow, forming many side shoots, the plants do not bloom.

Soft mosaic virus. Light mottling on the leaves, light strokes on the flowers.

Ring spot virus. Leaves have chlorotic concentric rings.

Clove banding virus. The leaves have whitish, yellow, brown stripes or strokes.

The carriers of these viruses are many species of aphids and nematodes.

yellow dwarf virus Luke. Allium virus 1. At the base of the leaves and on the flower arrows - short yellow stripes. The leaves turn yellow, the arrows are bent. Flower heads become smaller, bulbs are small, plants have a dwarf appearance.

On the apple trees Several types of viruses have been identified:

Apple mosaic virus. On the leaves - a light mosaic in the form of small irregular cream or yellow spots. In summer, in place of spots - necrosis. Sometimes there is a deformation of the leaf blade.

The rosette virus. Rosettes of very small ugly leaves are formed on the shoots.

drooping branch virus. The plant has a "weeping" appearance. The shoots droop, the wood in them is soft due to the lack of lignification processes. The turgor in the cells is lowered, there is a lag in growth.

Panicle or bushiness virus. On separate branches there is an excessive development of numerous shoots.

Fruit cracking virus. Late flowering, few flowers, single fruits, affected shoots die off. On the fruits - stellate cracks around the calyx.

Ring spot virus astr. Causes the formation of chlorotic rings and zigzag lines on the leaves of aster - Chinese callistefus, zinnia, perennial aster.

Viral content- this is information that spreads over the Internet at an increasing speed through transmission from user to user (according to the "word of mouth" principle). This is content created using viral marketing techniques and consisting of bright, extraordinary, urgent, emotional, interesting and attention-grabbing materials that voluntarily the audience is divided.

The recipients of the materials participate in the distribution of viral content, and they themselves involve new participants in the "viral process" and increase the reach of the audience.

When using viral content, the concept of "virality" is often mentioned as the ability of information to spread in social networks by voluntary transfer of materials between people. One might even say that virality- this is "friendly spam" in social networks, the basis of social viral marketing and viral content in particular.

The material costs of the webmaster for the formation of viral information are small, and the resulting effect is huge. Viral content attracts traffic, helps promote and cite the brand, and encourages people to be active. However, a single and trouble-free scheme for creating viral content has not yet been invented.

Viral Content Forms

The form of expression is different: text, video, photo, animation, audio. But the best effect is obtained by combining, combining visual information with text and links. For example, schemes work well:

"Picture + Text";
"Video + Text";
"Picture + Text + Link";
"Video + Link + Text".

But combining a picture and a video in one note reduces the visibility of the material and confuses users.

When creating viral materials, it is important to take into account the effect of the first emotional impact on the recipient, which usually lasts no more than 2-3 seconds. If during this short time the information is noticed, arouses interest and emotions, then the probability of reading (and, consequently, dissemination) of the message will increase.

Principles of Viral Content

When developing and shaping a viral message, you need to decide on the form and topic. We will talk about the latter below, but will it be enough? No. In addition to answering the question “What to write about?”, It is important for you to know the answer to an equally significant question - “How to write?”. So, you will have to:

Viral content in examples

No one will be able to determine in advance whether this or that content will become viral. The only way to assess the virality of information in social networks is through testing and experiments. However, a number of common qualities, rules, criteria have been identified that increase the likelihood of a viral effect.

You only need one. Arouse genuine interest, touch the feelings of the recipient, hurt his emotions - only this will encourage him to content distribution. In this case, you need not only to choose any popular topic, but also send a message to the desired target group. Let's take a look at how this might look like with examples.

Extraordinary, unusual topics

When people come across unusual topics, they start to think. And interest is the first factor in the impact of viral information. Perhaps, until this moment, a person did not know about the existence of some things, did not pay attention to it. Having met an unusual note on a social network, people begin to think, to be interested in the question.

For example, a note about the desperation of wedding photographers on the social network VKontakte. The topic, which no one thought about, gained more than 4,000 thousand likes and 500 reposts in less than a day. This is despite the fact that the post is not 100% unique, it was published earlier in other communities and was already familiar to people, but in a different form:

Contests, promotions and marathons. Free prizes and gifts

Note: free prizes and gifts have long been successfully used to collect subscribers on large blogs, social resources like YouTube, in social networks. The technology is very simple (gift for action), and therefore understandable and effective!

Users take note of useful information, add it to bookmarks, and re-read it again. In order not to lose valuable materials and records, people save them on the pages, ensuring the virality of the content.

Humor, laughter, "jokes", blunders, funny photos and videos

Humor is a universal theme that is not limited by any language or geographical boundaries. About 40% of all viral content is formed on the topic of humor, and the reader has come across such notes more than once. Sometimes the theme of positivity and humor is used as an addition to other publications.

Everyone without exception likes high-quality humor and positive, but this topic it is very difficult to link with sales, with the commercial goals of a web project. If the task is to sell, then humor is used as an addition to attract attention.

We give an example right away - this entry gained more than 300,000 views in a few days!

Breaking news, important announcements

Distribution of this type of content usually involves mature people who follow the news. The younger generation is less affected by urgency statements.

Breaking breaking news is often negative, which is difficult to use to sell goods or services. If the news is positive, consistent with the theme of the project, they must be used to form viral content. Firstly, the news will be of interest to readers, and secondly, it will contribute to the spread of links and mentions of a commercial resource.

To find examples of such content, just go to the pages of any major news portal or web media representation.

Little-known facts, discoveries of science

Information of a pseudo-educational nature can be found in any of the topics and used to create viral content. People like the truth, they like to learn new things, they are interested in discoveries and facts. Facts are good already because they are concretized, accurate and indisputable.

Absurd, controversial and resonant materials

Such news is very actively discussed by users, but not always in a positive light. Absurd and controversial information, as you might guess, will have both supporters and opponents. The more controversial the issue is raised in the news, the higher the virality and virality.

The negative side here is the increase in the number of negative reviews. It is extremely difficult to predict the reaction of users to controversial information of resonant content, but its virality is guaranteed. Linking this topic to sales and commerce will also be difficult.

For example, a video with the theory that we live in a black hole has received over 300,000 views. The topic, of course, is very controversial, but interesting.

Shocking cases, stories, photos and videos

Like absurd news, shocking information will not be to the taste of all recipients. With the inept use of this viral theme, the opposite effect can work. It often happened that, due to shocking materials, communities on social networks lost thousands of their unprepared subscribers in an instant, in whom the information aroused discontent and indignation.

And if one person agrees to repost such news, then the other will rush to scroll through, close, unsubscribe or disable them in the feed. A good example is the issuance of YouTube for the query "SHOCK":

Motivational and educational content

Viral motivational and educational content is saved by people for further use. Over time, reposts become more and more, materials diverge on the social network.

These can be articles, courses, webinar recordings, training invitations, books, podcasts, infographics, links to educational websites, motivational images, photos and animations. Like other topics, this area is popular in social networks. Especially if the information being disseminated clearly encourages you to repost.

The publication of materials on the user's personal page makes the information available and open to the social environment of the person.

An example is a high-quality motivational video about the benefits of entrepreneurship over work. Over 350.000 views.

Emotional and sensual content for girls

Obviously, if the reader is a girl, then she herself will be able to name a lot of examples of viral posts of similar content. For the male half of readers, we emphasize that here the information is exclusively feminine, sensual, emotional.

It can be stories, videos, images on the topic of love, relationships, romance. Here you can also use the topics of psychology, family, infidelity, motherhood, marriage, weddings, as well as related areas. An example of such a publication, which gained more than 1000 reposts and 3500 likes in a couple of hours:

Selections, lists, collections, lists

Selections can be made any, in accordance with the theme of the project. For example, let's take a look at a movie community post with a selection of 10 puzzle movies. In a couple of hours, more than 590 people shared the recording, and this is only within 1 single group. The number of reposts is growing every minute:

Let's summarize

Any content can become viral if the conditions are met, which are divided into 2 stages (creation and publication):

Creating Viral Content. When developing potentially viral materials, you need to think through to the smallest detail:
- type of information (photo, video, text, etc.);
- subject (according to the theme of the promoted project);
- format (news in the group, note on the profile wall, publication of the YouTube channel);
- emotional reference point (what emotions and feelings the content should evoke).
Posting content on social media(sowing information) - selection of ideal conditions:
- publication time. The peak of the accumulation of the target active audience most often falls in the evening;
- placements. From popular communities, thematic profiles or channels, where the target active audience is in abundance, viral content will spread faster and easier.

All 6 factors are critical to a successful launch viral content. We especially emphasize the activity of the audience, because exactly active people participate in the transfer of materials, make reposts and put likes, follow the links. Without at least one of the conditions, it is unlikely that high virality will be achieved. Namely, this factor predetermines the degree of dissemination of information in social networks.

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:

Airborne. Respiratory viral infections are transmitted by the retraction of mucus particles splattered during a sneeze.
Parenterally. In this case, the disease passes from mother to child, during medical manipulations, sex.
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:

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.
reproduction rate. After entering the body, the cells are affected one by one, providing the necessary nutrient medium.
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.

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.
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.
Meningitis. Occurs with an enterovirus and is more common in children.
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.
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.

Flu and cold. Their signs are: weakness, fever, sore throat. Antiviral drugs are used, when bacteria are attached, antibiotics are additionally prescribed.
Rubella. The eyes, respiratory tract, cervical lymph nodes and skin are affected. It spreads by airborne droplets, accompanied by high fever and skin rashes.
Piggy. The respiratory tract is affected, in rare cases, the testes are affected in men.
Yellow fever. Harms the liver and blood vessels.
Measles. Dangerous to children, affects the intestines, respiratory tract and skin.
. Often occurs in the background of other problems.
Polio. Penetrates into the blood through the intestines and breathing, with brain damage, paralysis occurs.
Angina. There are several types, characterized by headache, high fever, severe sore throat and chills.
Hepatitis. Any variety causes yellowness of the skin, darkening of the urine and colorless feces, which indicates a violation of several bodily functions.
Typhoid. rare in modern world, affects the circulatory system, can lead to thrombosis.
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.
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:

Hantavirus. The causative agent is transmitted from rodents, causes various fevers, mortality in which ranges from 12 to 36%.
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.
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.
. It causes diarrhea, the treatment is simple, but in underdeveloped countries 450 thousand children die from it every year.
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.
. Mortality is estimated at 50%, intoxication, rash, fever, and lymph node damage are characteristic. Distributed in Asia, Oceania and Africa.
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.
Rabies. Transmitted from warm-blooded animals, affects the nervous system. After the appearance of symptoms, the success of treatment is almost impossible.
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.
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 necessitates the search for new drugs, but present stage development of medicine, most measures are being 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

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

Viruses (biology deciphers the meaning of this term as follows) are extracellular agents that can reproduce only with the help of living cells. Moreover, they are able to infect not only people, plants and animals, but also bacteria. Bacterial viruses are called bacteriophages. Not so long ago, species were discovered that amaze each other. They are called "satellite viruses".

General characteristics

Viruses are a very numerous biological form, as they exist in every ecosystem on planet Earth. Their study is carried out by such a science as virology - a section of microbiology.

Each virus particle has several components:

Genetic data (RNA or DNA);

Capsid (protein shell) - performs a protective function;

Viruses have a fairly diverse shape, ranging from the simplest helical to icosahedral. Standard sizes are about one-hundredth of the size of a small bacterium. However, most specimens are so small that they are not even visible under a light microscope.

They spread in several ways: viruses living in plants are moved by insects that feed on grass juices; Animal viruses are carried by blood-sucking insects. Wu are transmitted large quantity methods: airborne or sexually, as well as through blood transfusion.

Origin

In our time, there are three hypotheses of the origin of viruses.

Briefly about viruses (on the biology of these organisms, our knowledge base, unfortunately, is far from perfect) you can read in this article. Each of the above theories has its drawbacks and unproven hypotheses.

Viruses as a form of life

There are two definitions of the life form of viruses. According to the first, extracellular agents are a complex of organic molecules. The second definition says that viruses are a special form of life.

Viruses (biology implies the emergence of many new types of viruses) are characterized as organisms on the border of the living. They are similar to living cells in that they have their own unique set of genes and evolve based on the method of natural selection. They can also reproduce, creating copies of themselves. Since viruses are not scientists, they do not consider them as living matter.

In order to synthesize their own molecules, extracellular agents need a host cell. The lack of their own metabolism does not allow them to reproduce without outside help.

Classification of viruses according to Baltimore

What are viruses, biology describes in sufficient detail. David Baltimore (Nobel laureate) developed his classification of viruses, which is still a success. This classification based on how mRNA is formed.

Viruses must form mRNA from their own genomes. This process is necessary for self-nucleic acid replication and protein formation.

The classification of viruses (biology takes into account their origin), according to Baltimore, is as follows:

Viruses with double-stranded DNA without RNA stage. These include mimiviruses and herpeviruses.

Single-stranded DNA with positive polarity (parvoviruses).

double-stranded RNA (rotaviruses).

Single-stranded RNA of positive polarity. Representatives: flaviviruses, picornaviruses.

Single-stranded RNA molecule of double or negative polarity. Examples: filoviruses, orthomyxoviruses.

Single-stranded positive RNA, as well as the presence of DNA synthesis on an RNA template (HIV).

Double-stranded DNA, and the presence of DNA synthesis on an RNA template (hepatitis B).

Life span

Examples of viruses in biology are found at almost every turn. But everyone life cycle runs almost the same. Without a cellular structure, they cannot reproduce by division. Therefore, they use materials that are inside the cells of their host. Thus, they reproduce a large number of copies of themselves.

The virus cycle consists of several stages that are mutually overlapping.

At the first stage, the virus is attached, that is, it forms a specific connection between its proteins and the receptors of the host cell. Next, you need to penetrate the cell itself and transfer your genetic material to it. Some species also tolerate proteins. Thereafter, loss of the capsid occurs and the genomic nucleic acid is released.

Human diseases

Each virus has a specific mechanism of action on its host. This process involves the lysis of cells, which leads to their death. At the time of death a large number cells begin to function poorly throughout the body. In many cases, viruses may not harm human health. In medicine, this is called latency. An example of such a virus is herpes. Some latent species can be beneficial. Sometimes their presence triggers an immune response against bacterial pathogens.

Some infections may be chronic or lifelong. That is, the virus develops, despite the protective functions of the body.

Epidemics

Horizontal transmission is the most common type of virus spread among humanity.

The rate of transmission of the virus depends on several factors: population density, the number of people with poor immunity, as well as the quality of medicine and weather conditions.

Body protection

The types of viruses in biology that can affect human health are innumerable. The very first protective reaction is innate immunity. It consists of special mechanisms that provide non-specific protection. This type of immunity is not able to provide reliable and long-term protection.

When vertebrates develop adaptive immunity, special antibodies are produced that attach to the virus and make it harmless.

However, not all existing viruses acquired immunity develops. For example, HIV constantly changes its amino acid sequence, so it escapes the immune system.

Treatment and prevention

Viruses in biology are a very common phenomenon, so scientists have developed special vaccines containing "killer substances" for the viruses themselves. The most common and effective method of control is vaccination, which creates immunity to infections, as well as antiviral drugs that can selectively inhibit viral replication.

Biology describes viruses and bacteria mainly as harmful inhabitants of the human body. Currently, with the help of vaccination it is possible to overcome more than thirty viruses that have settled in the human body, and even more - in the body of animals.

Preventive measures against viral diseases should be carried out on time and with high quality. To do this, humanity must lead a healthy lifestyle and try to possible ways boost immunity. The state should arrange quarantines in time and provide good medical care.

plant viruses

Artificial viruses

The ability to create viruses under artificial conditions can have many implications. The virus cannot die out completely as long as there are bodies sensitive to it.

Viruses are weapons

Viruses and the biosphere

On the this moment extracellular agents can "boast" the largest number individuals and species living on planet Earth. They perform important function by regulating the number of populations of living organisms. Very often they form symbiosis with animals. For example, the venom of some wasps contains components of a viral origin. However, their main role in the existence of the biosphere is life in the sea and ocean.

One teaspoon of sea salt contains approximately one million viruses. Their main purpose is to regulate life in aquatic ecosystems. Most of them are absolutely harmless to flora and fauna.

But these are not all positive qualities. Viruses regulate the process of photosynthesis, therefore increasing the percentage of oxygen in the atmosphere.

17.05.2020

A computer

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