In the past decade, reports of disease have soared in the United States and have resulted in increased illness and death, as well as increased media attention and litigation. Over 5000 cases were reported to CDC of legionellosis last year, with almost all cases reported to be individuals hospitalized with Legionnaires’ disease and almost half being cared for in intensive care units. The fatality rate may exceed 10 percent. Although Legionnaires’ disease cannot be clinically distinguished from other types of pneumonia, most hospitalized patients with pneumonia are not tested for the disease. Most public health efforts have focused on on detecting, investigating and controlling outbreaks of legionellosis, yet only 4% of reported cases are identified as part of an outbreak.