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.
On the other hand, people will argue that viruses do not have any structure to their cells (which even simple living organisms have), they do not have the ability to make their own chemical products and need a host cell to do that for them and that is why they can not reproduce without a host cell.