This post continues the discussion of the National Academies of Sciences management of Legionella in water systems report. Chapter one serves as an introduction that outlines how Legionella spreads, as seen in Part 1. This post focuses on the many possible sources of infection. Legionnaires’ disease has been known to have outbreaks at places where there is both biofilm growth and the potential for aerosolization. Many such areas exist in man-made structures, including components of heating, ventilation, and air conditioning (HVAC) systems such as cooling towers and humidifiers; indoor plumbing (called premise plumbing) including outlets such as showerheads and faucets; as well as spas and hot tubs. Additional places that have been known to infect individuals are fountains, misters, nebulizers, car washes, and industrial wastewater treatment plants. As seen in the 2015 outbreak in New York City building and industrial scale cooling towers are known centers for outbreaks of Legionnaires’ disease. Cooling towers remove heat from recirculating water used in water-cooled chillers, heat pumps, air compressors, and other equipment. During this process, these towers may generate bacteria-laden aerosols that drift away from the building or facility and are then inhaled by people working and living in the building as well as passersby. Exposure can also occur indoors if the downdraft from cooling towers is transported into building interiors, via air intakes or infiltration. In the United States, there are estimated to be two million cooling towers including both individual and industrial towers. Although in the United States the average hotel occupancy is about 66 percent, it can fluctuate seasonally between less than 50 percent to more than 75 percent, creating significant potential for water stagnation. Legionella is known to thrive in premise plumbing when the water is stagnant, and there are more than 5 million hotel rooms in the country. The total length of premise plumbing is thought to be more than 6 million miles. Another major type of a man-made environment that can generate Legionella risk are recreational water features, both outdoor and indoor. These include swimming pools, hot tubs, hot-spring baths, fountains and water parks. At these such locations, biofilms can form on surfaces and contaminated aerosols can be generated. Recreational sources have resulted in several Legionnaires’ disease outbreaks. [1] Click here for a free consultation! THE MATERIALS ON THIS WEBSITE HAVE BEEN PREPARED BY JULES ZACHER, P.C. FOR INFORMATIONAL PURPOSES ONLY AND ARE NOT LEGAL ADVICE OR A SUBSTITUTE FOR LEGAL COUNSEL. [1] https://www.nap.edu/catalog/25474/management-of-legionella-in-water-systems