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Mode of Transmission
Refers to the way(s) in which infectious agents travel from reservoirs to hosts.
- Modes of Transmission includes Contact, Droplet, Airborne, and various combinations of these routes.
- Contact: The most common form of transmission, whereby persons become exposed to pathogens through contact with a person who is infected, or coming into contact with an object that has been contaminated. Also see Direct Contact and Indirect Contact
- Droplet: Transmission that occurs as result of large, respiratory droplets containing infectious agents that come into contact with the mucous membranes (e.g. eyes, nose, mouth/throat membranes) of a susceptible host. Droplets can be expelled during coughing, sneezing, laughing and some types of medical procedures (e.g. suctioning), but, as result of their size, typically only travel up to two meters before falling to the ground. Droplets have the potential to land on medical equipment and environmental surfaces, which creates risk for Indirect Contact transmission. Influenza is an example of an infection that spreads through Droplet and Contact transmission.
- Airborne: Transmission that occurs as result of tiny, respiratory droplet nuclei particles (1-5 microns in diameter), which enter a susceptible host through inhalation. Droplet nuclei can be expelled during all activities that pass air out of the nose/mouth (e.g. talking, laughing, coughing, etc.) as well as during aerosol-generating medical procedures (e.g. intubation, suctioning, sputum induction, etc.). Once in the air, particles can remain suspended for long periods of time. Tuberculosis is an example of an infection that spreads through Airborne transmission.
References:
Peel Public Health. (2011). The Chain of Infection. Retrieved from: http://www.peelregion.ca/health/discon/htmfiles/take-control/2011/sec2/2-1-The-Chain-of-Infection.pdf
Centres for Disease Control. (2017). Transmission-Based Precautions. Retrieved from: https://www.cdc.gov/infectioncontrol/basics/transmission-based-precautions.html