Viruses (synonym: informireba, ultravirus, filterable virus) - submicroscopic infectious agents being strict intracellular parasites. There are viruses animals, plants and bacteria (see Bacteriophage). The composition of the virus is a nucleic acid that carries genetic information. Nucleic acid surrounded by a protein shell that protects it from external influences and ensures penetration of the virus into the cell. The shell of some viruses also contains polysaccharides and lipids. The viruses belonging to the world of living beings is manifested in the course of the infectious cycle of viruses, consisting of the following stages: 1) adsorption of the virus on the surface of the host cell as a result of interaction between certain components of the shell of the virus and specific surface of the cell (the specificity of this interaction determines the ability of each type of the virus to infect only one particular type of cell tropism of the virus. For example, the rabies virus exclusively affects nerve cells, and the smallpox virus multiplies only in certain parts covering tissues); 2) the penetration of the virus into the cell (at this stage of the nucleic acid of the virus is released from proteins and other components of membranes and enters the cytoplasm of the host cell); 3) education of the child components of viral particles (this happen two processes: (a) reproduction of viral nucleic acid replication, (b) a synthesis of viral proteins. For the implementation of both processes are used synthetic and power devices host cell); 4) the Assembly of finished particles viral progeny (a subsidiary of the molecules of the nucleic acid of the virus interacts with the components of viral envelope, resulting in the formation of Mature virus particles); 5) lysis (dissolution of cell walls from inside with the help of special enzymes viral origin) and exit viral progeny into the environment. In some cases, the release of viral particles is not accompanied by lysis of cells.
Describes the sequence characteristic of the so-called political development cycle of viruses. Some viruses (moderate bacteriophages, virus polyoma and others), extending into the cage, take her in a symbiotic relationship, forming the state of virojenie or lysogeny (see).
Viruses are the agents of a large group of viral diseases of humans, animals and plants. Among the human viral diseases include influenza, smallpox, rabies, Botkin's disease, yellow fever, tick-borne and Japanese encephalitides , etc. also Proved the viral etiology of many tumors. The spread of viral infections occur in a variety of ways. For example, a virus polio enters the human body from water or food; the yellow fever virus and Japanese encephalitis is transferred by mosquitoes; tick-borne encephalitis - tongs; the rabies virus enters the body through the bite of an animal suffering from rabies; for influenza virus gateway serve the respiratory tract.
Pathogenesis and clinical manifestations of viral diseases are very diverse. In labs viruses grown in tissue culture (see), in the organism of experimental animals, in chicken embryos. On artificial nutrient media viruses cannot be obtained, therefore, special methods of diagnostics agents of viral diseases, among them the most important are serological reactions (see Virological tests). In the treatment and prevention of viral diseases essential immunological methods (see vaccine therapy, Interferon, Seroprevalencia, Serotherapy).