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How do people get Legionnaires' disease?

People can catch legionnaires’ disease by inhaling small droplets of water, suspended in the air, containing the bacteria. Certain conditions increase the risk from legionella, including:

  • water temperature between 20–45 °C, which is suitable for growth

  • a source of nutrients for the organism e.g. presence of sludge, scale or fouling

  • stored and/or re-cirulated water

  • creating and spreading breathable droplets of water, e.g. aerosol created by a cooling tower, or water outlets