There are seven principle characteristics of living organisms (some say there are ten) that determine whether something is living or not. Those characteristics are Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, and Nutrition. The only one of those characteristics exhibited by viruses is Reproduction, but they cannot reproduce on their own. I virus is nothing more than a packet of genetic code that requires a host cell to complete the processes of replication for it in order to reproduce. Lacking the other 6 (or 9) characteristics, a virus cannot be considered living.