Final answer:
The term 'Contact' describes a person or animal known to have been exposed to a disease; not all exposure leads to infection, depending on the pathogen and host defenses.
Step-by-step explanation:
The term that refers to a person or animal known or believed to have been exposed to a disease is Contact. When someone comes into exposure with a potential pathogen, such as the virus that causes chickenpox, there is a risk of developing the illness if infection occurs. This is often an initial infection before the virus enters latency in the host. For a disease to manifest, a series of stages must occur starting from exposure, leading to adhesion (colonization), invasion, and finally infection. Not all contacts result in infection, as the pathogen must overcome the body's defenses and cause damage to establish disease.