The coronavirus epidemic that swept across our planet has stirred up the whole world – this has not happened for a long time! Previously, villages died out from the spread of dangerous diseases, cities died out much less often, and only a few times the pandemic swept Europe. Today, a person is so mobile that some new virus instantly spreads around the world, creating a threat to absolutely the entire 8 billion population.

"Virus" in Latin is a poison. Viruses were discovered more than a century ago, and since then several thousand of their species have been identified, although according to some assumptions their number may number tens of millions. This is the simplest organic form containing DNA or RNA molecules in the protein envelope. They are a kind of parasites, since they cannot reproduce outside the cell. They affect all types of living organisms, including plants.

Usually, when viruses enter a living organism, they cause an antigen – induced reaction of the immune system, and the body begins to fight the alien-most often successfully. But some viruses can avoid the body's immune response (HIV, hepatitis).

Most of the viruses that have invaded the cell lead to its death. Sometimes the embedded virus does not manifest itself in any way, and then the disease turns into a chronic form.

Where do new types of viruses come from all the time?
Do not seriously consider conspiracy theories that all modern viruses are created in top-secret military laboratories. The virus copes perfectly without them. An excellent example is HIV, which has a huge rate of reproduction and mutation, tens of thousands of times greater than that of bacteria. Therefore, the creation of appropriate drugs is very difficult – viruses can mutate in just weeks, developing resistance to drugs.

It is the enormous speed of reproduction and mutation that underlies the constant appearance of new viruses. Among the many descendant viruses, there is a great variety in RNA or DNA sequences, and the most adapted of them to disguise themselves from the body's immune system almost completely replace their parents within a very short time (in this regard, viruses behave in full accordance with the theory of evolution).

As for the regions where new viruses spread, these are mainly countries in Africa and Asia. At the same time, the viruses of new strains themselves appear quite evenly in the world, and even more in northern latitudes. But in poor and economically underdeveloped countries, countries with constant conflicts, countries with a huge population density (like China or India), the health system cannot work so effectively as to instantly respond to the appearance of new viruses and prevent epidemics developing from local outbreaks of diseases.