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.
Viruses are very simple microbes, they can't do much by themselves. Viruses need a host, another living organism that gives them everything they need to work. Viruses take any chance they can to find a host. They get inside the host's cells and take it over. Viruses use the host cells machinery to make lots of copies, so many that the cell bursts and infects other cells around it!