- See also changes related to Pathogen, or pages that link to Pathogen or to this page or whose text .
- Bacteria : A major group of single-celled microorganisms.
- Epidemiology : The branch of demography that studies patterns of disease in human or animal populations.
- Fungus : A eukaryotic organism, classified into the kingdom Fungi, that is heterotrophic and digest their food externally, and may be a yeast, mold, or mushroom.
- Infectious disease : In broad terms, diseases caused by living organisms; also a subspecialty of internal medicine concerned with the treatment of such diseases
- Protozoa : A subkingdom consisting of unicellular organisms that are the simplest in the animal kingdom. Most are free living. They range in size from submicroscopic to macroscopic. Protozoa are divided into seven phyla: Sarcomastigophora, Labyrinthomorpha, Apicomplexia, Microspora, Ascetospora, Myxozoa, and Ciliophora.
- Virus : Please do not use this term in your topic list, because there is no single article for it. Please substitute a more precise term. See Virus (disambiguation) for a list of available, more precise, topics. Please add a new usage if needed.
- Infectivity : The potential ability of micro-organisms or parasites to cause disease in man, animal, or plant under specified conditions.
- Virulence : The degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host (Medical Subject Headings)