The entry, establishment, and multiplication or persistence of an infectious agent in a host.
An infection occurs when an infectious agent such as a bacterium, virus, fungus, or parasite enters a host and successfully establishes itself. The body may eliminate the agent without causing noticeable illness, or the infection may lead to an infectious disease with symptoms, signs, or tissue damage.
Infection does not necessarily mean that a person is visibly sick or has symptoms. Some infections are asymptomatic, while others can cause severe disease. Infections may be acquired through direct contact, respiratory droplets or aerosols, contaminated food or water, sexual contact, vectors, or other routes.
COMMONLY CONFUSED WITH
- Inflammation: a biological response that can result from infection but can also occur without infection.
- Infectious disease: disease caused by an infection; an infection does not always produce disease.
- Contamination: the unwanted presence of an infectious agent or other substance where it does not belong; contamination does not necessarily mean infection has occurred.
SEE ALSO
