What is a virus
Viruses are particles that live on the border of living organisms and chemical compounds. They have the ability to create crystalline structures that are characteristic for inanimate matter and, on the other hand, are able to multiply and spread diseases, including upper respiratory tract infections.
Most viruses are much smaller than bacteria, which makes them impossible to observe under a standard optical microscope. They are composed of nucleic acids (DNA or RNA) and capsid (the protein coat in which the genetic material of the virus is located).
Viruses do not have their own reproductive organs. They are obligatory parasites, which means that in order to propagate they have to use cells of other organisms. Viruses put their genetic information inside the host cell forcing it to produce (replicate) the virus.