Chain of Infection Flashcards
Triad Model
interaction of agent host and environment
habitat
in which the agent normally lives, grows and multiplies
reservoir examples
humans, animals, the environment
animal reservoirs
transmitted from animal to animal with humans as incidental hosts
portal of exit
the path by which a pathogen leaves its host, usually corresponds to the site where the pathogen is localized
Modes of Transmission
how an agent is passed along
direct
indirect
direct modes of transmission
direct contact
indirect modes of transmission
airborne
vehicle borne
vector born
direct Transmission
an infectious agent is transferred from a reservoir to a susceptible host by direct contact or droplet spread
can also refer to contact with soil or vegetation harboring the agent
Droplet Spread
refers to spray with relatively large short-range aerosols produced by sneezing, coughing or even talking
Indirect Transmission
refers to transfer of an infectious agent from a reservoir to a host by suspended air particles, inanimate objects (vehicles) or animate intermediaries (vectors)
Airborne Transmission
when infectious agents are carried by dust or droplet nuclei suspended in air
droplet nuclei are..
dired residue of less than 5 microns in size - can remain in the air for a long time
Vehicles
indirectly trasmits an infectious agent through food, water, biologic products and fomites (inanimate objects)
can be apssive
can also be the environment the agent grows in.
NOT LIVING
vectors
carries an infectious agent through purely mechanical means or may support growth or changes in the agent
NEEDS TO BE LIVING
but biologic transmission requires the disease to undergo maturation in an intermediate host before transmission
