In the chain of infection, which term denotes the route by which pathogens are passed from the reservoir to the next host?

• A. Transmission
• B. Reservoir
• C. Portal of exit
• D. Portal of entry

Answer: (A)

Transmission is the term that describes the route by which pathogens move from the reservoir to the next host. It covers the various ways the agent can travel—direct contact, droplets, airborne spread, vehicles like contaminated water or food, or vectors such as insects. This distinguishes it from other parts of the chain: the reservoir is where the pathogen lives or multiplies, the portal of exit is how it leaves the reservoir or infected host, and the portal of entry is how it gets into a new host. Since the question pinpoints the passage of pathogens from one host (or source) to another, transmission best captures that moving-through-space and through mechanisms aspect of spread.