Speaker:	Dr. Mark W. LeChevallier
Institution:	Dr. Water Consulting, LLC
Seminar Date:	Thursday, Apr. 29th, 2021, 3:30-4:50 PM

Legionnaires’ disease, the illness primarily caused by Legionella pneumophila, has increased by over 500 percent since 2000 and has become the most commonly identified cause of drinking water outbreaks in the U.S. During the 2013-2014 reporting period, Legionella infections were responsible for all reported deaths due to drinking water-associated illnesses. Presently approximately 60 species consisting of about 70 serogroups of Legionella are known, with some serotypes primarily associated with severe (Legionnaire’s disease) or the self-limiting mild (Pontiac fever) forms of human disease. Although outbreaks are typically associated with the plumbing systems of large buildings and cooling towers, most Legionella cases are not associated with outbreaks.

Drinking water and reclaimed water distribution systems have been shown to be reservoirs for Legionella. Factors contributing to Legionella growth include elevated ambient temperatures, scale and sediment accumulation, corrosion, absence of disinfectant residuals and presence of biodegradable and assimilable organic carbon (i.e. BDOC and AOC). Free living amoebae serve as hosts and reservoirs of Legionella bacteria in water systems, so understand the ecology of these organisms is important in the management of Legionella in water.

The presentation will give an overview of the Legionella organisms, occurrence in water, factors contributing to growth and survival, sensitivity to disinfection, and their relationship to free living amoebae. Factors contributing to increased risk, as well as best management practices, will be summarized. Guidance has been developed to help proactively address and mitigate potential risks from Legionella in drinking water and reclaimed water. The lecture will end with a series of recommendations for future research, and policy development.