What is the chain of infection?

For a health care-associated infection to be transmitted from one person to another, conditions must be right. A person might be sick, but if they are isolated, then the infection won’t be transmitted. Likewise, if a person is exposed to an infection but has an immune system strong enough to fight it off, then, again, the infection won’t be transmitted. For a health care-associated infection to be transmitted between individuals, a specific set of circumstances must be present. This set of circumstances is known as the chain of infection and comprises the following six links in the chain:

• Infectious agent.
• Reservoir.
• Portal of exit.
• Mode of transmission.
• Portal of entry.
• Susceptible host.

Each of these items is discussed in greater detail in separate entries.