Pathogenic infections

In biology, a pathogen in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ. The term pathogen came into use in the 1880s. Typically, the term is used to describe an infectious microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus. Small animals, such as certain kinds of worms and insect larvae, can also produce disease. However, these animals are usually, in common parlance, referred to as parasites rather than pathogens.