A pathogen or infectious agent (colloquially known as a germ) is a microorganism—in the widest sense, such as a virus, bacterium, prion, or fungus—that causes disease in its host. The host may be an animal, a plant, or even another microorganism. There are several substrates including pathways whereby 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.