An infectious agent is a biological agent capable of entering a host and causing an infection.
Infectious agents include bacteria, viruses, fungi, parasites, and certain other biological agents. They can enter the body through routes such as the respiratory tract, digestive tract, broken skin, sexual contact, contaminated food or water, or the bites of infected organisms.
Whether exposure results in infection depends on factors involving the agent, the host, and the circumstances of exposure. The presence of an infectious agent therefore does not always mean that disease will occur.
QUICK FACT
Infection does not always mean illness. A person can become infected without developing noticeable symptoms.
COMMONLY CONFUSED WITH
Microorganism: A microorganism is defined primarily by its microscopic size; an infectious agent is defined by its ability to cause infection. Some infectious agents, such as viruses, do not fit neatly into the traditional definition of a microorganism.
SEE ALSO
- Microorganism
- Infection
- Contamination
- Pathogen
- Exposure