Difference between a virus and a parasite

A Parasite is something that is living off our body or in your body and benefits by deriving nutrients at the host's expense. Such as a leech. 
A virus is an invective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host. Such as H1N1

Technically, viruses are similar to obligate intracellular parasites as they lack the means for self-reproduction outside a host cell, but unlike parasites, viruses are generally not considered to be true living organisms.