If all living organism are made up of cell then why not virus?

Question

 I am asking this question because when they enter a cell they become living organism. And the cell theory states that all living organism are made up of cell.

Answer 1

So, you are asking why viruses are not considered to be made of cells, and you suggest that since all living things are made of cells, and viruses are lying (after host invasion), then they should be considered to be made of cells. Correct?

 

I would profit that viruses are NOT made out of cells, because (a) they can’t maintain homeostasis, (b) they don’t grow, and (c) they can’t perform metabolic functions and make energy.  These are primary requirements of living cells.

 

So, I would say that viruses are not cells, and shouldn't be considered "living", even when inhabiting a host.  Although, it is more complicated because it has been shown that a virus can actually be infected by another virus, and so maybe they are living things.