You shouldn't go out in public when you're contagious
Jen has been sick at home with the flu for several days and is still having symptoms.
Jen wants to get some soup in order to feel better.
Jen orders delivery and instructs them to leave it at the door.
Jen goes out to the store while sick to pick up some cans of soup.
Other people have been protected from exposure to the flu.
Jen spreads the illness to others.