Viruses are very small particles that cause disease in living things. They are so small (20-500 nanometers) that even bacteria outnumber them! Viruses cannot be seen with a classical microscope, so scientists have to use photographs taken with a more powerful electron microscope to study them.
Viruses are very difficult to obtain in the laboratory, creating conditions for their growth and reproduction, since they strictly need the presence of living matter for this. In 2005, French scientists tried to conduct an experiment to «resurrect» an ancient virus, but it was unable to survive in modern realities.
It is impossible to determine the exact time of the origin of the virus, but they are believed to be incredibly ancient. Tracking their appearance is unrealistic, because they do not leave any traces behind them, and they also infect absolutely all types of living organisms, that is, not only people, but also animals, plants, algae, fungi and even bacteria. Interestingly, life itself on earth was born thanks to viruses: from the fact that they penetrated into bacteria, the first cells were formed.
Viruses are parasites, that is, those who are completely dependent on the organism in which they are located. They are not always active — some viruses may not manifest themselves for up to 10 years, as does the hepatitis virus, for example. Some scientists believe that many «useless» formations in the human body are all the same viruses that could take root in the body at one of the stages of evolution.
There are several groups of viruses, each of which causes certain groups of diseases. For example, one group is responsible for diseases such as measles, chickenpox or smallpox, another for diseases of the nervous system, and the third works with internal organs, provoking influenza and various inflammations.
Scientists still do not know a truly effective method to fight viruses, since antibiotics do not work on them. Someone even says that it is viruses — the true kings of our planet — that appeared incredibly long ago, very simple, but at the same time very effective. It is believed that it is best to train the human immune system so that it learns to recognize viruses on its own and fight back.