Answer:
JoAnn is the reservoir in the chain of transmission. The mucus from her cough is the portal of exit in the chain of transmission.
Step-by-step explanation:
Infection can be defined as the penetration and development or multiplication of an infectious agent in the body of man or another animal. The infection may trigger some clinical manifestations, being in this case called infectious disease.
A reservoir in the transmission chain can be understood as the habitat of an infectious agent in which it lives, grows and multiplies. In this case, as the infectious agent is using JoAnn's body as a habitat to develop, we can say that in the chain of infection JoAnn is the reservoir.
The exit portal in an infection transmission chain is where the body expels the microorganism that is the infectious agent. In this case, the exit portal is JoAnn's sneeze and cough.