The influenza exhibit was a scientific demonstration of influenza, more commonly known as the flu, an infectious disease that is caused by an influenza virus. The exhibit was displayed at the Hill Valley Science Exposition in 1933.
History[]
Emmett Brown told Marty McFly that the exhibit wasn't properly contained, and it leaked into the concession stands. Presumably, the negative publicity surrounding this incident caused the end of the science expo, making the 1933 event its last.