A pathogen ( pathos, "suffering, passion" and γενής genēs (-gen) "producer of") or infectious agent — in colloquial terms, a germ — is a microorganism such as a virus, bacterium, prion, or fungus, that causes disease in its animal or plant host. There are several substrates including pathways wherein pathogens can invade a host; the principal pathways have different episodic time frames, but soil contamination has the longest or most persistent potential for harboring a pathogen.