The video shows 10 people coming into the restaurant, with one singled out as an "infected" person. A fluorescent substance only visible under black light is applied onto that person's hands, representing germs from a cough or a sneeze. Each participant then goes about the buffet as they normally would, not considering a potential contamination.
At the end of the video, the participants are cast under black lights illuminating where the "infection" has spread.
The substance, used to signify the germs, can be seen on food, serving utensils and platters, and even on the faces of some of the participants.