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Symbiotic Relationships and Disease



competitive relationship among organisms where one inhibits or suppresses the growth of others


relationship in which one species benefits but the other neither benefits nor is harmed


presence of an outside organism in or on nonliving matter

convalescence period

stage of the disease process when symptoms disappear. It is considered a recovery period, when host strength is regained.

decline phase

stage of disease when symptoms begin to abate and the pathogen population begins to decline


disorder or condition resulting in harm to an organism's structure or function and disturbing its homeostasis (the body's processes to physiologically regulate its internal environment)

horizontal transmission

spread of pathogens between members of the same species not in a parent-offspring relationship

incubation period

initial stage of the disease process before symptoms become apparent and the pathogen is actively replicating


invasion and multiplication of pathogens, or disease-causing organisms, within the host body

infectious disease

disease resulting from infection

latent disease

disease that is not clinically active, or without signs or symptoms of disease in the host. The pathogenic agent remains dormant within a cell of the host body.


relationship in which both organisms benefit from the relationship

noncommunicable disease

infectious disease that is not spread from host to host

noninfectious disease

disease not caused by an infectious agent or pathogen


typically harmless microbe that under the right circumstances will cause infection


relationship where one organism benefits to the detriment of the other


capacity to cause disease

prodromal phase

stage of the disease process when symptoms first become apparent


ecological relationship between two or more organisms that live in direct contact with one another


relationship among organisms that allows for the creation of an effect that neither could create on its own

vertical transmission

spread of pathogens from mother to offspring before or during birth


relative extent or severity of disease caused by a pathogen. It refers to its ability to colonize host tissue and the severity of harm or disease it causes.

virulence factor

feature enabling a pathogen to cause disease by releasing toxins, invading host cells and tissues, suppressing the host's immune responses, or otherwise damaging the host