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 five 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.