Final answer:
The chain of infection is defined by source, mode of transmission, and susceptible host.
Step-by-step explanation:
The components that define the chain of infection are source, mode of transmission, and susceptible host.
Source refers to the origin of the pathogen, such as an infected individual or contaminated object.
Mode of transmission refers to the way in which the pathogen is transferred from the source to the susceptible host, such as through direct contact, droplets, or contaminated surfaces.
Susceptible host is a person or organism that is vulnerable to being infected by the pathogen.