In biology, a pathogen (Greek: πάθος, pathos "suffering", "passion" and -γενής, -genēs "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ.[1]

The term pathogen came into use in the 1880s.[2][3] Typically, the term pathogen is used to describe an infectious microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus.[4][5][6] Small animals, such as helminths and insects, can also cause or transmit disease. However, these animals are usually referred to as parasites rather than pathogens.[7] The scientific study of microscopic organisms, including microscopic pathogenic organisms, is called microbiology, while parasitology refers to the scientific study of parasites and the organisms that host them.

There are several pathways through which pathogens can invade a host. The principal pathways have different episodic time frames, but soil has the longest or most persistent potential for harboring a pathogen.

Diseases in humans that are caused by infectious agents are known as pathogenic diseases. Not all diseases are caused by pathogens, such as black lung from exposure to the pollutant coal dust, genetic disorders like sickle cell disease, and autoimmune diseases like lupus.

  1. ^ Thomas L (September 1972). "Germs". The New England Journal of Medicine. 287 (11): 553–5. doi:10.1056/NEJM197209142871109. PMID 5050429.
  2. ^ "Pathogen". Unabridged (Online). n.d. Retrieved August 17, 2013.
  3. ^ Cite error: The named reference casadevall2014 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Alberts_2002 was invoked but never defined (see the help page).
  5. ^ "MetaPathogen – about various types of pathogenic organisms". Archived from the original on 5 October 2017. Retrieved 15 January 2015.
  6. ^ "Bacteria". Basic Biology. 18 March 2016.
  7. ^ Gazzinelli-Guimaraes PH, Nutman TB (2018). "Helminth parasites and immune regulation". F1000Research. 7: 1685. doi:10.12688/f1000research.15596.1. PMC 6206608. PMID 30416709.

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