Final answer:
The chain of infection is defined by three main components: (a) the source of the infection, the mode of transmission, and the susceptible host.
Step-by-step explanation:
The components that define the chain of infection include a source, a mode of transmission, and a susceptible host. The source is the origin of the infectious agent, the mode of transmission is how the agent is spread (through direct contact, airborne particles, etc.), and the susceptible host is an individual who is at risk of becoming infected due to a lack of immunity or other factors.
To break the chain of infection, understanding each component is crucial in implementing effective control measures.