What is the reservoir in the chain of infection?

In order to be a viable organism, an infectious agent needs a place to live. This place is called the reservoir, which is the second link in the chain of infection.

Pathogens can use many things as reservoirs, including humans, animals, the soil, and water. Reservoirs can also be non-organic items such as toothbrushes and doorknobs. A human who serves as a reservoir for a pathogen does not always become ill as a result of the pathogen. Reservoirs can simply be carriers of the pathogen without suffering any ill effects from its presence.