Why Can't We Eliminate Legionnaires' Disease?

As I previously wrote, Legionnaires’ Disease was first identified in 1976 at a hotel in Philadelphia where members of the Philadelphia State American Legion were staying. About 200 Legionnaires were struck with what appeared to be severe cold symptoms, and 29 ultimately died. The bacteria, Legionella pneumophila, was identified as the causative agent and determined to have spread from the hotel’s air conditioning system. The CDC published “Legionnaires’ Disease” as the official name of the disease. 

Legionnaires’ Disease is a type of pneumonia with symptoms including fevers, chills, muscle aches, and coughs. It is contracted by inhaling water droplets containing Legionella bacteria. Legionnaires’ Disease occurs more often in older adults and people with weakened immune systems. It does not spread from person to person or by drinking water, only by inhaling mist from water.  

Legionella are typically found in freshwater, such as rivers and lakes, but they multiply and can pose a human health hazard in warm, stagnant water, including plumbing systems, cooling towers, heating, ventilation, and air conditioning (HVAC) systems, humidifiers, and hot tubs. They multiply and hide in the biofilms that form within pipes, where they are dispersed through tiny water droplets. Legionella can be difficult to control because they not only hide in biofilms but within microorganisms in the water, such as amoebae, which are not killed by disinfection.   

Controlling Legionella involves regular cleaning and disinfection of cooling towers. This requires acid cleaning to remove scale and rust, disinfection with chlorine, chlorine dioxide, or ozone, and stripping of biofilm and loosening of deposits. It is recommended at least once a year and costs approximately $10,000.