Any of various submicroscopic agents that infect living organisms, often causing disease, and that consist of a single or double strand of RNA or DNA surrounded by a protein coat. Unable to replicate without a host cell, viruses are typically not considered living organisms, A computer program or series of commands that can replicate itself and that spreads by inserting copies of itself into other files or programs which users later transfer to other computers. Viruses usually have a harmful effect, as in erasing all the data on a disk, A harmful or destructive influence