Legionellosis is usually an acute respiratory tract infection that begins 2-14 days after exposure to Legionella spp. Signs of the disease can include a high fever, chills, and cough, in addition to head and muscle aches. Since symptoms are similar to those seen in other forms of pneumonia, the diagnosis is rarely obvious and can be difficult to make. Available diagnostic tests include direct fluorescent antibody staining, culture, polymerase chain reaction on sputum, and urine antigen detection.
"Pontiac Fever," a milder illness associated with Legionella bacteria, is characterized by fever and myalgias without pneumonia. It typically occurs a few hours to two days after exposure.
Legionella bacteria are found naturally in the environment, usually in water and grow best in warm conditions such as hot tubs, cooling towers, hot water tanks, large plumbing systems, or the air-conditioning systems of large buildings. Person-to-person transmission does not occur.