Describe the structure of viruses. What is the importance of viruses in human life?

Viruses are non-cellular organisms, obligate parasites that cannot reproduce on their own, do not have a metabolism, and do not grow. Outside the host cells, they exist in the form of varion crystals. They consist of a single nucleic acid (DNA or RNA) and a protein capsid. For humans, all viruses, without exception, are dangerous, cause various diseases: AIDS, influenza, hepatitis, measles, rubella, smallpox, encephalitis, poliomyelitis, rabies, etc. But they also have scientific significance.