July 27, 1976 - Air Force veteran Ray Brennan became the first of 34 people to die from a mysterious illness at a Legionnaire's convention in Philadelphia.
221 people fell terribly ill with extreme flu-like symptoms. As the death toll climbed, doctors still could not figure out what the hell was going on.
As the Centers for Disease Control and Prevention scrambled to diagnose and treat the victims, one theory was that a long-feared swine flu epidemic had finally hit the United States. This led to the prompt passage of a nationwide vaccination program.
Eventually it became clear that the culprit was an especially deadly bacteria that until then had been undiscovered. Researchers found it lurking in a cooling tower at the hotel where the Legionnaires convention was held, but soon warnings were issued for similar breeding grounds all around the world. One popular spot where the Legionellosis bacterium has been known to thrive is inside lighted indoor fountains - especially when the lights are submerged in the water.
The research into Legionairres Disease continues. Each year between 10,000 and 50,000 cases pop up in the United States.