The Water Deer (Hydropotes inermis) is a usually solitary animal, besides the rutting months, and a good swimmer. There exist two subspecies: the Chinese Water Deer (Hydropotes inermis inermis) and the Korean Water Deer (Hydropotes inermis argyropus).
Viruses lack most of the internal structure and machinery which characterize 'life', including the biosynthetic machinery that is necessary for reproduction. In order for a virus to replicate it must infect a suitable host cell.
So, a virus must have a host cell (bacteria, plant or animal) in which to live and make more viruses. Outside of a host cell, viruses cannot function. For this reason, viruses tread the fine line that separates living things from nonliving things.