In biology, 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, viroid, or parasite that causes disease in its host. The host may be a human, an animal, a plant, a fungus, or even another micro-organism.

In biology, 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, viroid, or parasite that causes disease in its host. The host may be a human, an animal, a plant, a fungus, or even another micro-organism.