A virus is a type of pathogen; it is a single strand of a pathogen. As a result, a virus is not the same thing as a pathogen.
A virus, also known as a virion, is usually composed of a nucleic acid molecule that is engulfed by a protein or lipid (fat) coat, called a capsid. In addition, a virus contains a complete set of DNA and is only able to infect a live host by inserting its DNA, leading to the lyse (death) of the host cell. Once the host cells have been infected with the virus, they will begin to produce new cells with a set of the virus’s DNA, instead of their own.