Viruses only really have one trait that is shared with living organisms. That is they mutate.
The current classification of life states that in order to be considered alive living things must:
1. grow (viruses don't)
2. be able to respond to a stimulus (viruses can't)
3. reproduce (viruses cannot reproduce on their own - they need the host cell to make more viruses)
4. be made of cells (viruses are not made of cells - they are only made of RNA or DNA surrounded by a protein).
5. metabolize (viruses don't take in or require any food)
6. change (viruses can mutate).
