Viruses do not have a cellular structure. They are the simplest life form on our planet. Viruses are a transitional form between living and nonliving matter. Viruses are so small that they can only be seen with an electron microscope.
Viruses are intracellular parasites, and outside the cell they do not show any properties of living things (they do not grow, do not eat, do not produce energy, they do not have a metabolism).
Viruses differ from inanimate matter in two properties:
- are able to reproduce similar forms to themselves (multiply);
- possess heredity and variability.
Viruses are arranged very simply. They are made up of genetic material (RNA or DNA) enclosed in a protein shell called a capsid.
Having penetrated into the cell, the virus changes its metabolism, directing all the activity of the cell to the production of viral nucleic acid and viral proteins. Self-assembly of viral particles from synthesized nucleic acid molecules and proteins occurs inside the cell. Until the moment of death, a huge number of viral particles have time to be synthesized in the cell. Ultimately, the cell dies, its membrane bursts, and viruses leave the host cell.
The evolutionary origin of viruses is still unclear. Most scientists assume that viruses are cells or their fragments, which, in the course of adaptation to parasitism, have lost everything that “can be done without”, except for their hereditary apparatus in the form of nucleic acid and a protective protein coat.
Viruses are the cause of dangerous diseases. Examples of viral diseases are rabies, swine fever, mosaic plant disease. Viral diseases include such dangerous human diseases as influenza, hepatitis, AIDS, measles.
AIDS is a viral disease
The human immunodeficiency virus (HIV), which is the cause of acquired immunodeficiency syndrome (AIDS), was discovered in the United States in 1981. According to the WHO, more than 60 million people have been infected with this virus since the beginning of the epidemic.
HIV infects white blood cells, primarily helper lymphocytes, which are involved in the immune response to infection. Immunity is impaired, blood cells cease to recognize disease-causing agents in the body, and a person becomes vulnerable to any infectious disease. More than half of AIDS patients die from pneumonia, which a healthy person usually suffers without serious consequences.
Ways of transmission and prevention of AIDS
Most often, HIV is acquired through semen or blood. 90% of those infected are sexually infected. Moreover, the more sexual partners there are, the higher the likelihood of infection. The virus spreads rapidly among drug addicts due to the use of the same syringe. You can get infected if you come into contact with the blood of a person infected with the virus, for example, when dressing a wound. It is possible to get infected through blood transfusions if it has not been tested for HIV. Another way of infection is the transmission of the virus from a sick mother to a child through the placenta or in breast milk.
This virus does not spread by airborne droplets and by shaking hands.
Strict adherence to the rules of prevention will help protect against HIV infection:
- limiting sexual intercourse and using condoms;
- use of disposable syringes, compliance with the rules for sterilization of reusable instruments;
- thorough screening of donated blood for HIV.