Viruses cause different diseases. It very dangerous. And that dangerous are creatures, substances? What virus? He, in general, living? Scientific determination says of that a virus is a noncellular pathogen that can be reproduced only into living cages. Viruses exist anywhere that there is though some life. It is considered that they exist on Earth from times of evolution of living cages. And if the virus of flu frightens us already not very strongly, then the periodically nascent new forms of viruses inspire fear on humanity. Bird flu pork, fever of Эбола, virus of immunodeficit of man, - much what we were frightened lately. Now is a coronaviruses. Let us know about viruses as many as possible and we will understand, how so they are frightful, as they are painted.