In the chain of infection, which component describes the route by which a pathogen enters a new host?

• A. Portal of Entry
• B. Reservoir
• C. Mode of Transmission
• D. Portal of Exit

Answer: (A)

The route by which a pathogen enters a new person is the portal of entry. It describes the entry point and path the organism uses to access the body's tissues, such as inhalation into the lungs, ingestion into the gastrointestinal tract, contact with broken skin, or access through mucous membranes like the eyes or nose. This is why protective measures target these entry routes—masks, hand hygiene, proper wound care, and safe food handling help block entry. Other terms in the chain refer to different steps: the reservoir is where the pathogen lives, the mode of transmission is how it travels from one place to another, and the portal of exit is how it leaves the host to begin the process again.