In the chain of infection, the portal of exit is:

• A. Any body opening on an infected person that allows pathogens to leave
• B. A body opening on a host that allows pathogens enter
• C. The reservoir where pathogens reside
• D. The mode of transmission

Answer: (A)

The idea being tested is how infections spread from one person to another. The portal of exit is the route by which pathogens leave the infected person to reach someone else. Paths include natural openings and secretions such as the mouth, nose, mucous membranes, wounds, skin, or body fluids; for example, coughing or sneezing can release infectious droplets, while blood or other fluids can carry pathogens out through an open wound or seepage. This exit point is what allows transmission to begin.

This is different from the portal of entry, which is how a new person becomes infected, or from the reservoir, which is where the pathogens live and multiply, and from the mode of transmission, which is the method by which the pathogen is carried to the next host.