Canadian officials should check any people coming in if they have the disease so it doesn't come into Canada and infect people in Canada
This is an example of Homeostasis or Adaptation.
Stimulus is anything that results in a response. It can be external or internal. Stimuli is the plural form of it. For example:
"There can be one stimulus in this article."
There can be 2 or more stimuli in this article."
In a chemical reaction, the substances that undergo change are called reactants