What is link two of the chain of infection?

• A. Reservoir host
• B. Portal of Exit
• C. Infectious Agent
• D. Portal of Entry

Answer: (A)

In the chain of infection, the second link is the reservoir. The reservoir is the place where the infectious agent normally lives, grows, and multiplies—this can be a person, an animal, or the environment. The reservoir may or may not show illness, but it serves as the source from which the pathogen can spread to others. The idea is that the pathogen needs a place to persist, so controlling or eliminating the reservoir reduces transmission.

For example, a person with an active infection can be a reservoir for illnesses like influenza; animals can serve as reservoirs for rabies; and contaminated water can be a reservoir for cholera. The other parts—portal of exit (how the agent leaves the reservoir) and portal of entry (how it enters a new host)—are separate links that come after the reservoir in the chain, and the infectious agent is the actual organism causing the disease, which is the first link.