Infection

Article By:

Pierce, Marcia M. Department of Biological Sciences, Eastern Kentucky University, Richmond, Kentucky.

Last reviewed:June 2022

DOI:https://doi.org/10.1036/1097-8542.343000

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• Infection, published January 2020:Download PDF Get Adobe Acrobat Reader

The entrance, growth, and multiplication of a microorganism or pathogen in the body of a host. Infection may or may not result in the establishment of a disease process, depending on many variables including the pathogen involved, the health of the host, and how the pathogen enters and establishes itself in the host body. Some infections are asymptomatic, producing no detectable pathologic effects, while others cause severe symptoms and can cause mortality in the host. Hosts vary greatly; for example, bacteria can be infected by bacteriophages, plants by plant viruses or fungi, and humans can be infected by a wide range of pathogen types, including viruses, bacteria (Fig. 1), protozoans, fungi, and prions. Infection can be distinguished from infestation, which is the invasion of a host by higher organisms, such as parasitic worms (helminths). See also: Bacteria; Bacteriophage; Death; Disease; Fungal virus; Fungi; Infectious disease; Medical bacteriology; Medical mycology; Medical parasitology; Opportunistic infections; Pathogen; Plant; Plant pathology; Prion; Prion disease; Protozoa; Virus

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