If you've seen enough episodes of Dateline, you sort of know how this is going to play out.
West Side Story 1961
Science fiction story about youths in mid-century New York City afflicted by a neurological illness that causes eruptions of spontaneous dancing and singing. A cautionary tale about the importance of properly funding public health initiatives, that is especially chilling in light of recent vaccination controversies.
The Day of the Dolphin 1973
Better than it sounds, but possibly dumber than you can fathom. My memory is shaky, but it seemed like eighty percent of the dialogue was squealed by horrific talking dolphins. The major highlight is seeing George C. Scott trying to communicate with a talking dolphin in a kind of primitive baby talk, and treating it very seriously.