Legionnaires’ disease is the deadliest waterborne-illness in the United States, killing about one in 11 people infected. Reported cases of the pneumonia-like disease, spread by inhaling droplets contaminated with the Legionella bacteria, are rapidly rising, up four and a half times since 2000. Present in the natural environment, the bacteria flourish in building plumbing systems, which are the front lines for controlling the spread of the disease.