Viral diseases arose in ancient times, but virology as a science began to develop at the end of the 19th century.
In 1892, the Russian scientist-botanist DI Ivanovsky, studying mosaic disease of tobacco leaves, found that this disease is caused by the smallest microorganisms that pass through fine-pored bacterial filters. These microorganisms are called filterable viruses (from Latin virus - poison). Later it was shown that there are other microorganisms passing through bacterial filters, so the filtered viruses began to be called simply viruses.
Weakened families, in whose cells there are many dead larvae, are treated with antibiotics. There are no drugs that can completely cure viral diseases. However, diseased insects are treated with agents that increase the body's defenses and limit the development of the virus.
Prevents virus replication and encourages bee development in spring. Treatment is carried out in the morning or in the evening when all the bees are in the hive. Biomycin. In the body of insects weakened by the virus, pathogenic microflora is actively developing. Therefore, it is recommended to use biomedicine for infected families in the first half of summer. A dose of syrup is given after 50 years.
A great contribution to the study of viruses was made by Soviet virologists: M.A.Morozov, N.F.Gamaleya, L.A. Zilber, M.P. Chumakov, A.A. Smorodintsev, V.M. Zhdanov, and others.
Viruses are non-cellular form existence of living matter. They are very small. According to the figurative expression of VM Zhdanov, "their size in relation to the size of average bacteria can be compared with the size of a mouse in relation to an elephant." It became possible to see viruses only after the invention of the electron microscope.
These preparations are available as a powder, which is sprayed onto the surface of the cake in quantities of 5 g and 2.5 g, respectively. Also used are preparations containing plant components: garlic, black pepper, horsetail, pine extract, St. John's wort, echinacea purple, eucalyptus and others. They contribute to the rapid development of families, strengthening their health and improving the immunity of bees.
A large, multi-colored microcosm spreads all around us, but we never see it with the naked eye. Each of us has been the target of many attacks in various viruses, starting with a nasty haze. By the way, colds can cause more than 100 types of viruses - rhinoviruses and coronaviruses. A lesser known fact is that every person's body is formed and then destroyed tumor cells... Fortunately, in most people, the immune system prevents malaria. However, viruses focus not only on humans, but also on animals, plants and fungi.
Currently, many methods are used to study viruses: chemical, physical, molecular biological, immunobiological, and genetic.
All viruses are subdivided into infecting humans, animals, insects, bacteria and plants.
Viruses have a wide variety of forms and biological properties, but they all have common structural features. Mature virus particles are called virions.
It lasts for several decades. Viruses are professionally characterized as microscopic boxes of proteins that contain genetic material. A nucleic acid chain surrounds the protein capsules. However, unlike other microbes, viruses are neither dead nor alive. It forms a special world, which is the border between inanimate substances and living organisms. Professionally, viruses are marked inactive - a sign that they show no signs of life until they attack a suitable host.
They can be completely dried. Their protein packs will be transformed into crystals of a similar salt, so they will last for decades in dry conditions. Then it is enough for them to dissolve in water and live immediately. Viruses as such cannot even reproduce! They need to attack and control another cell to play them. It inserts nucleic acid or genetic material into it.
Unlike other microorganisms containing both DNA and RNA, the virion contains only one of the nucleic acids - either DNA or RNA.
The nucleic acid of viruses can be single-stranded and double-stranded. Almost all viruses containing RNA have single-stranded RNA in their genome, and those containing DNA have double-stranded DNA. In accordance with two types of genetic substance, viruses are divided into RNA- and DNA-containing. DNA-containing families include 5 families, RNA-containing ones - 10 families.
As a concrete example, let's put in a rhyme and see what a drunken virus does to our olfactory organ. One tiny rhinovirus is enough for infection. It attacks cells and thus finds a suitable environment for reproduction. After going into the cell, she will make her make copies. The infection causes the mucous cells to produce more fluid, which is irritating and makes them sneeze. Then, an unimaginable number of viruses are scattered into the air to find other victims. However, you cannot infect your pet, such as a dog or cat.
* (Here are data on only some of the viruses pathogenic for humans.)
Virion structure... In the center of the virion there is a nucleic acid, which is surrounded by a capsid (from the Greek kanca - box). The capsid is composed of protein subunits called capsomeres. A mature virus is a nucleocapsid in chemical structure. The number of capsomeres and the way they are packed (Fig. 52) are strictly constant for each type of virus. For example, the poliomyelitis virus contains 32 capsomeres, while the adenovirus contains 252 capsomeres. Capsomeres can be stacked in the form of a polyhedron with uniform symmetrical edges - cuboidal shape (for example, adenovirus). Spherical styling is typical for influenza viruses. There may be a type of symmetry in which the nucleic acid has the form of a spring around which capsomeres are laid, in which case the virus has a rod-shaped form - a virus that causes tobacco leaf disease.
Rhinoviruses, like other relatives, usually attack only one type of host; in humans, rhyme. Viruses attack bacteria! The role of "enslaved" cells is often bacteria. Many people cannot tell the difference between a virus and a bacterium. Recall that bacteria that are found in different environments are the smallest self-sufficient living organisms - the most numerous on Earth. For an idea: just one teaspoon of garden soil holds at least five billion of them. If we baked bacteria at the tip of a needle, which were then enlarged with advanced technology to the size of a spacecraft, we could see the enlarged bacteria with the naked eye with tremendous effort.
The phage has a complex type of symmetry: the head is cuboidal, and the process is rod-shaped (sperm-shaped) (see Fig. 21, 22).
Thus, depending on the method of packing, viruses are subdivided into cuboidal, spherical, rod-shaped and spermatozoid forms.
In addition, bacteria become the target of virus attacks that look for a suitable host. T 4 slowly lands on bacteria, just like a spacecraft on the surface of a planet. Immediately after planting, bacteria inject their genes into the bacterial cell. Genes are actually chemical instructions that force bacteria to create new viruses.
A new generation is born within 20-30 minutes, and then the bacterial cell wall dissolves, and fresh viruses can go out into the vicinity to find new victims.Almost every type of bacteria is parasitized by one or more viruses called bacteriophages. Some of them do not harm plants, others are slower, sometimes even threatening. The aggressive carrier of viruses between plants is many small insects, especially aphids. The thorn feeds the stem, and the juices are beaten by possible viruses. Another plant can then remove these viruses from its digestive tract.
Some viruses with more complex structures have a shell called peplos. It is formed when the virus leaves the host cell. In this case, the viral capsid is enveloped by the inner surface of the cytoplasmic membrane of the host cell and one or more layers of the supercapsid envelope are formed. Only some viruses have such an envelope, for example, the viruses of rabies, herpes, encephalitis. This shell contains phospholipids, which are degraded by ether. Thus, by acting on ether, it is possible to distinguish a virus with peplos from a virus with a "naked capsid".
Infections in mammals and birds are caused by the so-called coronaviruses. Viral disease is no exception. An infectious disease is a disease caused by various types of microorganisms, especially bacteria and viruses. They live inside or on the human body, and they like to spread from one person to another. Many infectious diseases are not serious, and the immune system will soon be recommended. Unfortunately, infections are much more dangerous.
Depending on how we distinguish: local infections - diseases only in a small area. When a disease spreads over a large area, we are talking about an epidemic. The worst pandemic is the incidence across the continent or the world. If the disease is of viral origin, the more difficult is that, unlike bacteria, it does not produce antibiotics. This is a serious illness as it usually affects people who are already suffering from another illness. Rubella usually does not harm the body, but it can damage the fetus in pregnant women.
In some viruses, capsomeres in the form of thorns (these thorns are blunt) protrude from the outer lipid layer of the envelope. These viruses are called peplomers (eg influenza virus, see Figure 52).
The nucleic acid of the virus is a carrier of hereditary properties, and the capsid and the outer shell carry protective functions, as if protecting the nucleic acid. In addition, they facilitate the entry of the virus into the cell.
The distribution methods are varied. Sleep: If it causes the hepatitis B virus, it is fatal. Marbury disease: death caused by filovirus. How do we share viruses? Each virus can infect a specific range of cells, which allows it to bind to a specific molecular structure in a membrane or wall at a so-called receptor. A specific molecular structure is also involved in the virus. The virus can only be infected by cells that carry certain receptors.
Every healthy organism infects itself with a cold virus infection. This is possible thanks to the immune system - a personal doctor. This virus primarily overpowers our personal doctor - the immune system, also called immunological! The rule of good therapy is to kill the germ by attacking its weaknesses. The enzymes and proteins involved in the reproduction of the virus are delicate and can be destroyed chemicalsthat make up this drug.
Virus sizes... Viruses are measured in nanometers. Their magnitude fluctuates in a wide range from 15-20 to 350-400 nm.
Virus measurement methods: 1) filtration through bacterial filters with a known pore size; 2) ultracentrifugation - large viruses precipitate faster; 3) photographing viruses in an electron microscope.
First of all, we block the enzyme necessary for the virus to multiply. A viral enzyme - reverse transcriptase - is involved. This enzyme is sensitive to appropriate medicinesblocking its activity. Drugs that block the enzyme needed for the multiplication of the virus - reverse transcriptase, are divided into two groups.
The first is nucleoside analogs. The virus uses imitations of the complete defect contained in the preparation and cannot multiply. The second group of drugs is called non-nucleoside reverse transcriptase inhibitors. Secondly, we block the formation of the "body" of the new virus or its proteins.
The chemical composition of viruses... The amount and content of DNA and RNA viruses are not the same. In DNA, the molecular weight ranges from 1 · 10 6 to 1.6 · 10 8, and in RNA - from 2 · 10 6 to 9.0 · 10 6.
Proteins in virions are found in insignificant numbers, they consist of 16-20 amino acids. In addition to capsid proteins, there are also internal proteins associated with nucleic acid. Proteins determine the antigenic properties of viruses, and also, due to the dense packing of polypeptide chains, protect the virus from the action of host cell enzymes.
It is enough to use certain chemicals to prevent their proliferation. Thus, it will stop the virus from multiplying at the expense of humans. Many drugs have been registered that are effective in killing this enzyme. The body becomes defenseless against germs, which do not cause any disease symptoms under normal conditions.
The first is nucleoside analogs. The virus uses imitations of the complete defect contained in the preparation and cannot multiply. The second group of drugs is called non-nucleoside reverse transcriptase inhibitors. Secondly, we block the formation of the "body" of the new virus or its proteins.
Lipids and carbohydrates are found in the outer shell of complex virions. The host cell membrane is the source of lipids and carbohydrates. The polysaccharides that make up some viruses determine their ability to cause agglutination of erythrocytes.
Virus enzymes... Viruses do not have their own metabolism, so they do not need metabolic enzymes. However, some viruses have been found to have enzymes that facilitate their penetration into the host cell. For example, in the influenza A virus, neuraminidase was found, which cleaves off neuraminic acid contained in the membranes of animal cells (erythrocytes, etc.). Phages have lysozyme, which destroys the cell membrane, phosphatase, etc.
Detection of viral antigens... Viral antigens in infected host cells can be detected using immunofluorescence techniques. Preparations containing cells virus infectedare treated with specific immune luminescent sera. When viewed under a fluorescent microscope, a characteristic glow is observed in places where viral particles accumulate. The type of virus is determined by the correspondence of the specific luminescent serum that caused the luminescence.
The introduction of the virus into the cell, its interaction with the host cell and reproduction (reproduction) are composed of a series of successive stages.
Stage 1. Begins with the process of adsorption at the expense of the virion and cell receptors. In complex virions, receptors are located on the surface of the envelope in the form of styloid outgrowths (influenza virus), in simple virions, on the surface of the capsid.
Stage 2. Penetration of the virus into the host cell proceeds differently for different viruses. For example, some phages pierce the membrane with their process and inject nucleic acid into the host cell (see Chapter 8). Other viruses enter the cell by drawing in a viral particle with the help of a vacuole, that is, a depression is formed at the site of introduction in the cell membrane, then its edges are closed and the virus appears in the cell. This retraction is called viropexis.
Stage 3. "Stripping the virus" (disintegration). For its reproduction, the viral nucleic acid is freed from the protein covers (envelope and capsid) that protect it. The undressing process can begin during adsorption, or it can occur when the virus is already inside the cell.
Stage 4. At this stage, the replication (reproduction) of nucleic acids and the synthesis of viral proteins occurs. This stage occurs with the participation of the host cell's DNA or RNA.
Stage 5. Assembly of the virion. This process is facilitated by the self-assembly of protein particles around the viral nucleic acid. Protein synthesis can begin immediately after viral nucleic acid synthesis, or after an interval of several minutes or several hours. In some viruses, self-assembly occurs in the cytoplasm. Others have host cells in the nucleus. The formation of the outer shell (peplos) always occurs in the cytoplasm.
Stage 6. The release of the virion from the host cell occurs by percolation of the virus through the cell membrane or through a hole formed in the host cell (in this case, the host cell dies).
Types of virus-cell interaction... The first type, productive infection, is characterized by the formation of new virions in the host cell.
The second type - abortive infection - is that nucleic acid replication is interrupted.
The third type is characterized by the incorporation of viral nucleic acid into the DNA of the host cell; there is a form of coexistence of the virus and the host cell (virogeny). In this case, the synchronicity of viral and cellular DNA replication is ensured. In phages, this is called lysogeny.
Microscopic examination... With individual viral infections, specific intracellular bodies are observed in the cytoplasm or nuclei of the host's cells - inclusions that have diagnostic value (Babesh-Negri bodies in case of rabies, Guarnieri bodies in smallpox, etc.). The sizes of viral particles and bodies-inclusions can be artificially increased by special methods of processing preparations with mordant and impregnation (for example, the method of silvering according to Morozov) and observed with immersion microscopy. Smaller virions that lie outside the range of sight of an optical microscope are detected only with electron microscopy. There are different points of view regarding intracellular inclusions. Some authors believe that they represent a collection of viruses. Others believe that they arise as a result of the cell's reaction to the introduction of viruses.
Virus genetics... Modification (non-inherited changes) in viruses is caused by the characteristics of the host cell in which the virus reproduces. The modified viruses acquire the ability to infect cells similar to those in which they were modified. Different viruses manifest themselves in different ways. For example, the shape of "negative spots" (phage colonies) changes in phages.
Mutation - in viruses, it occurs under the influence of the same mutagens that cause mutation in bacteria (physical and chemical factors). A mutation occurs during nucleic acid replication. Mutations affect various properties of viruses, for example, sensitivity to temperature, etc.
Genetic recombination in viruses can occur as a result of simultaneous infection of a host cell with two viruses, while individual genes can be exchanged between two viruses and recombinants are formed containing the genes of two parents.
Genetic reactivation of genes sometimes occurs when an inactivated virus is crossed with a complete one, which leads to the salvation of the inactivated virus.
Spontaneous and directed genetics of viruses are of great importance in the development of the infectious process.
Resistant to environmental factors... Most viruses are inactivated by action high temperatures... However, there are exceptions, for example the hepatitis virus is heat-resistant.
TO low temperatures viruses are not sensitive, ultraviolet rays of the sun have an inactivating effect on viruses. Scattered sunlight acts on them less actively. Viruses are resistant to glycerol, which makes it possible to keep them in glycerin for a long time. They are resistant to antibiotics (during the cultivation of viruses, the test material is treated with antibiotics to suppress the bacterial flora).
Acids, alkalis, disinfectants inactivate viruses. However, some viruses inactivated with formalin retain their immunogenic properties, which makes it possible to use formalin to produce vaccines (rabies vaccine).
Susceptibility of animals... The range of susceptible animals for some viruses is very wide, for example, many animals are sensitive to rabies viruses. Some viruses only affect one species of animal, for example the canine plague virus only affects dogs. There are viruses to which animals are not susceptible - for example, measles virus, etc.
Organotropy of viruses... Viruses have the ability to infect certain organs, tissues and systems. For example, the rabies virus attacks the nervous system. The smallpox virus is dermatropic, etc.
Release of viruses into the environment... From a sick body, viruses can be excreted in the feces, for example, the poliomyelitis virus and other enteroviruses. The rabies virus is excreted in saliva, the influenza virus is excreted from the discharge of the nasopharyngeal mucosa, etc.
The main routes of transmission of viruses... Airborne droplets (influenza, smallpox), food (poliomyelitis, hepatitis A), contact and household (rabies), transmissible (encephalitis).
Antiviral immunity... The human body has an innate resistance to certain viruses. For example, humans are not susceptible to the canine plague virus. Animals are not susceptible to measles virus. In these cases, antiviral immunity is based on the absence of cells capable of supporting the reproduction of viruses.
Antiviral immunity is determined by both cellular and humoral defense factors, non-specific and specific. Non-specific factors. A powerful inhibitor of viral reproduction is a protein substance - interferon. IN healthy body it is contained in a small amount, and viruses contribute to the production of interferon and its amount increases significantly. It is non-specific as it blocks the reproduction of various viruses. However, it has tissue specificity, that is, cells of different tissues form different interferon. It is believed that its mechanism of action lies in the fact that it interferes with protein synthesis in the host cell and thereby stops the reproduction of the virus.
Specific factors of antiviral immunity include virus-neutralizing antibodies, hemagglutinating and precipitating antibodies.
Virus cultivation methods... Viruses reproduce only in viable cells. They are cultivated: in chicken embryos (Fig. 53), tissue cultures of humans and various animals, in the body of sensitive animals, susceptible arthropods.
In the first period of the development of virology, the main method for studying viruses was artificial infection of animals, but this method is complex, and besides this, animals turned out to be immune to many viruses.
Of great importance in the development of virology was the introduction of methods for the cultivation of viruses in chicken embryos and in the culture of human and animal tissue cells.
Chicken embryo infection... For the reproduction of viruses, chicken embryos of 7-12 days of age are used, incubated in a thermostat at 37 ° C. A necessary condition for the proper development of the embryo is compliance with a certain air humidity, which can be created by placing a vessel with water in the thermostat.
The suitability of a chicken embryo for infection is determined by the presence of movements of the embryo and a developed network of blood vessels on the chorion-allantoic membrane when scanning with an ovoscope.
Cultivation of viruses in chicken embryos is carried out in different places of the embryo, which is infected (see Fig. 53):
1) on the chorion-allantoic membrane,
2) into the allantoic cavity;
3) into the amniotic cavity;
4) into the yolk sac.
Chicken embryos are infected in a box using sterile instruments. Before infection, chicken embryos are wiped twice with a cotton swab moistened with alcohol.
Infection on the chorion-allantoic membrane. After disinfection, the eggs are carefully cut off a piece of the shell from the blunt end, the shell membrane is removed, and the chorion-allantoic membrane is found. Infectious material in an amount of 0.1-0.2 ml using a syringe or Pasteur pipette is applied to the chorion-allantoic membrane. After infection, the hole is closed with a cap and the gap between it and the chick embryo is filled with paraffin.
On the other side of the egg, write in pencil the name of the infectious material and the date of infection.
Infection into the amniotic cavity. The egg is ovoscoped and on the lateral side a site is selected where the chorion-allantois is devoid of large blood vessels. This area is marked with a pencil. The eggs are placed on a stand in a horizontal position, disinfected and a hole in the shell is pierced with a special sterile spear to a depth of 213 mm, through which a needle with infectious material is inserted at the same distance directly into the amniotic cavity. In order to prevent the injected liquid from flowing back, a puncture is made above the air bag, after which both holes are filled with paraffin.
Infection into the allantoic cavity. Infection is carried out in a darkened box. The air space is noted, the shell over the air space is disinfected and a syringe needle with the material is inserted through the hole in the shell towards the embryo. If the needle gets into the allantoic cavity, then the shadow of the embryo is displaced. After infection, the hole is filled with paraffin.
Infection in the yolk sac. The shell is disinfected. The egg is placed on the stand with the blunt end to the right so that the yolk sac is facing up. A hole is punctured above the air chamber in the center. A syringe needle is inserted through the hole in the shell in a horizontal direction to a depth of 2-3 mm, which enters the yolk sac. The material is injected in a volume of 0.2-0.3 ml. After the introduction of the material, the hole is waxed.
The temperature regime and the duration of incubation depend on the biological properties of the introduced virus.
Infected eggs are checked daily - ovoscopy to check the viability of the embryo. If the embryos die on the first day, then the cause of this is usually trauma during infection. Such eggs are derived from experience.
If it is necessary to separately examine each component of the embryo, the material is collected in a certain order: the allantoic fluid is aspirated, then the amniotic fluid, the chorion-allantoic membrane is cut, the amniotic membrane, the embryo, the yolk sac are separated, and only then the chorion-allantoic membrane is removed, separating it from the inner the surface of the shell. The presence of the virus in the infected embryo is determined by the characteristic changes in the chorion-allantoic membrane of the infected chicken embryo.
Viruses that do not have hemagglutinating activity are detected using CSCs.
To detect the virus in the allantoic or amniotic fluids of infected embryos, RHA is placed (hemagglutination is caused by allantoic or amniotic fluids or a suspension prepared from the chorion-allantoic membrane).
Culturing viruses in cell culture... For the accumulation of viruses in sensitive cell cultures, tissues of humans and various animals are used. The greatest practical application was received by single-layer cultures of primary trypsinized and transplanted cell lines.
Single-layer cell cultures are grown in glass flat mattress vessels. Cell suspension in a liquid nutrient medium at a temperature of 37 ° C makes it possible to obtain an "in vitro" layer of cells with a certain histological structure. The presence of viruses in tissue cultures is detected by the change (degeneration) of cells. The type of viruses is determined by neutralizing the effect of viruses by adding appropriate type-specific sera to the vaccinated material.
These methods allow for faster incorporation of research results and are more cost effective. In cases where viruses do not cause cytopathic action (degeneration) and do not develop in chick embryos, methods of infecting animals are used (see Chapter 11).
For the cultivation of viruses, continuous cells are used, which are more often obtained from cells of malignant tumors.
Single-layer cultures are obtained from human, chicken, animal embryos.
The advantage of single-layer cell cultures is the simplicity of the technique and ease of accounting.
The ability of cells to reproduce outside the body is related to the degree of tissue differentiation. Less differentiated tissues have a greater ability to proliferate (connective, epithelial tissue).
The essence of the methods for the preparation of primary tissue cultures is the destruction of the intercellular tissue and the separation of cells for the subsequent production of a monolayer.
Dissociation of cells is carried out by acting on the tissue of proteolytic enzymes, most often trypsin. Trypsin solution promotes the separation of cells while maintaining their ability to reproduce. Growing cell cultures requires a nutrient medium. The composition of the medium is complex, it includes a number of ingredients: amino acids, glucose, vitamins, mineral salts, coenzymes, etc. Tissue culture is obtained under strictly aseptic conditions. Antibiotics (500 U of penicillin and 250 U of streptomycin in 1 ml) are added to the medium to suppress the growth of bacterial flora.
The prepared tissue is poured with a 0.25% solution of warmed trypsin and incubated in a thermostat at 37 ° C. During incubation, the tissue is periodically stirred by rotating the flask. Trypsinized cells are centrifuged at 800-1000 rpm for 5 minutes.
Trypsinization and centrifugation are performed very carefully so as not to injure the cells. After centrifugation, the supernatant is removed, and the cell sediment is placed in a small volume of culture medium. To obtain a homogeneous mass, the suspension of cells is filtered through one layer of gauze in a funnel (sterile). The cell suspension is checked for sterility by inoculating 0.1 ml in 2 tubes with sugar broth.
The success of cell cultivation depends on the inoculation dose, therefore, after trypsinization, the cells are counted in the Goryaev chamber. After counting, the suspension of cells is diluted with a nutrient medium in such a way that 1 ml contains 500,000-1,000,000 cells and is poured into test tubes and mattresses. Tissue culture tubes are incubated in an incubator in an inclined position.
The inoculated cultures are examined daily under a low magnification microscope to determine the nature of their growth. Normal proliferating cells are light-colored and grow in a single layer. If cells are dark, grainy, and do not proliferate, which may be the result of contamination (poor handling of dishes or contaminated ingredients), then such cultures are removed from the experiment.
Changing the nutrient medium 2-3 days after sowing improves the intensity of proliferation.
Normal, well-proliferating cells are infected with the test material.
Transplanted cultures are mainly obtained from malignant tumors. Hela strain - culture of cervical cancer cells of a woman named Helena (obtained in 1950); strain Hep-2 isolated from a patient with laryngeal cancer. The growth of these cells is maintained in laboratories through successive passages. Their peculiarity lies in the fact that they reproduce for a long time. At present, these cells have gone through thousands of generations. In the process of passage, they lose some morphological and biochemical properties - they undergo mutations. However, they remain quite suitable for the cultivation of viruses in them. The culture of these cells is used by laboratories around the world.
Reproduction of the virus in cell culture occurs at different times, depending on the properties of the virus and the type of cells.
The presence of the virus is judged by the cytopathic effect. Cell degeneration is observed in the microscope. The time of cytopathic action and its nature depend on the dose and properties of the virus.
In some viruses, a cytopathic effect is detected after a few days (smallpox virus), in others, after 1-2 weeks (hepatitis virus, etc.).
Currently, there are already hundreds of viruses known to infect humans. Fight against viral infections carried out by different methods. Immunization is most effective. In this way, smallpox has been eliminated, and the incidence of poliomyelitis has been reduced. Social prevention is important in the fight against viral infections - the destruction of stray dogs (fight against rabies), personal prevention, etc.
However, these measures cannot ensure the elimination of all viral diseases... Scientists are persistently looking for ways to infect the virus without damaging the cell in which it is located.
Therefore, it is natural that in the program of the Communist Party of the Soviet Union virology is named one of the leading branches of natural science, which should receive priority development in the coming years.
Basic methods of research of viruses... 1. Reaction of hemagglutination, reaction of delayed hemagglutination, reaction of indirect hemagglutination. Complement binding reaction.
2. The reaction of neutralization of viruses in tissue culture.
3. Method of immunofluorescence.
4. Histological method - identification of inclusions (Babesh's little bodies - Negri - with rabies; Pashen's little bodies - with smallpox, etc.).
5. Biological method.