A pathogen ( pathos “suffering, passion” and -γενής -genēs “producer of”) in the oldest and broadest sense is anything that can produce disease, a term which came into use in the 1880s. Typically the term is used to describe an infectious agent such as a virus, bacterium, prion, fungus, or parasite that causes disease in its host. The host may be an animal, a plant, a fungus 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. Diseases caused by organisms in humans are known as pathogenic diseases. Some of the diseases that are caused by viral pathogens include smallpox, influenza, mumps, measles, chickenpox, ebola and rubella. Not all pathogens are necessarily undesirable to humans. In entomology, pathogens are one of the “three P’s” (predators, pathogens and parasitoids) that serve as natural or introduced biological controls to suppress arthropod pest populations.