how is legionnaires disease spread

Legionnaires' disease is primarily spread by breathing in small water droplets or mist that contain Legionella bacteria. These bacteria can grow and spread in various human-made water systems, such as showerheads, sink faucets, hot tubs, decorative fountains, large plumbing systems, and cooling towers of air- conditioning systems. People get infected when they inhale the mist with the bacteria. In addition to inhalation, infection can also occur less commonly when water containing the bacteria accidentally enters the lungs while drinking (aspiration). However, Legionnaires' disease does not generally spread from person to person. The bacteria grow best in warm water environments between 77°F and 113°F (25°C and 45°C). Factors that promote bacterial growth include slime buildup (biofilm), inadequate disinfectant, and stagnant water. These conditions are often found in building water systems, which can then become sources of outbreaks. Common places linked to Legionnaires' disease outbreaks include large buildings' water systems, hot tubs, cooling towers, hot water tanks, fountains, and whirlpool spas. In summary, Legionnaires' disease is spread through inhalation of water droplets containing Legionella bacteria from contaminated water systems, but is not spread person to person.