in Water Systems
Committee on Management of Legionella in Water Systems
Water Science and Technology Board
Board on Life Sciences
Board on Population Health and Public Health Practice
Division on Earth and Life Studies
Health and Medicine Division
A Consensus Study Report of
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This activity was supported by the Alfred P. Sloan Foundation under Grant No. G-2016-7288; Centers for Disease Control and Prevention under Contract No. 200-2011-38807, TO# 59; Department of Veterans Affairs under Contract No. VA250-16-C-0012; and Environmental Protection Agency under Contract No. EP-C-14-005, TO#22 and EP-C-14-005/68HE0C18F0876. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.
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Cover credit: Kyoko Kurosawa
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Suggested citation: National Academies of Sciences, Engineering, and Medicine. 2020. Management of Legionella in Water Systems. Washington, DC: The National Academies Press. http://doi.org/10.17226/25474.
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COMMITTEE ON MANAGEMENT OF LEGIONELLA IN WATER SYSTEMS
JOAN B. ROSE, NAE, Chair, Michigan State University, East Lansing
NICHOLAS J. ASHBOLT, University of Alberta, Edmonton, Canada
RUTH L. BERKELMAN, NAM, Emory University, Atlanta, Georgia
BRUCE J. GUTELIUS, New York City Department of Health and Mental Hygiene
CHARLES N. HAAS, Drexel University, Philadelphia, Pennsylvania
MARK W. LeCHEVALLIER, Dr. Water Consulting, LLC, Morrison, Colorado
JOHN T. LETSON, Memorial Sloan-Kettering Cancer Center, New York City, New York
STEVEN A. PERGAM, Fred Hutchinson Cancer Research Center and the University of Washington, Seattle
MICHÈLE PRÉVOST, Polytechnique Montréal, Canada
AMY PRUDEN, Virginia Polytechnic and State University, Blacksburg
MICHELE S. SWANSON, University of Michigan, Ann Arbor
PAUL W. J. J. van der WIELEN, KWR Water Research Institute, Nieuwegein, The Netherlands
LAN CHI NGUYEN WEEKES, La Cité, Ottawa, Canada
National Academies Staff
LAURA J. EHLERS, Study Director, Water Science and Technology Board
ANDREA HODGSON, Program Officer, Board on Life Sciences
KATHLEEN STRATTON, Scholar, Board on Population Health and Public Health Practice
ERIC EDKIN, Program Coordinator, Board on Earth Sciences and Resources
RAYMOND M. CHAPPETTA, Senior Program Assistant, Board on Earth Sciences and Resources
WATER SCIENCE AND TECHNOLOGY BOARD
CATHERINE L. KLING, Cornell University, Ithaca, New York
NEWSHA AJAMI, Stanford University, Stanford, California
JONATHAN D. ARTHUR, Florida Geological Survey, Tallahassee
DAVID A. DZOMBAK, NAE, Carnegie Mellon University, Pittsburgh, Pennsylvania
WENDY D. GRAHAM, University of Florida, Gainesville
MARK W. LeCHEVALLIER, Dr. Water Consulting, LLC, Morrison, Colorado
MARGARET A. PALMER, SESYNC – University of Maryland, Annapolis
DAVID L. SEDLAK, University of California, Berkeley
DAVID L. WEGNER, Jacobs Engineering, Tucson, Arizona
P. KAY WHITLOCK, Christopher B. Burke Engineering, Ltd., Rosemont, Illinois
ELIZABETH EIDE, Director
LAURA J. EHLERS, Senior Staff Officer
STEPHANIE E. JOHNSON, Senior Staff Officer
M. JEANNE AQUILINO, Financial/Administrative Associate
COURTNEY DeVANE, Administrative Coordinator
ERIC EDKIN, Program Coordinator
BRENDAN R. McGOVERN, Research Assistant/Senior Program Assistant (until December 2019)
RAYMOND M. CHAPPETTA, Senior Program Assistant (from January 2020)
Legionnaires’ disease arrived on the scene in dramatic fashion during the 1976 Philadelphia outbreak that included 182 cases of pneumonia and 29 deaths. Almost 40 years later, major outbreaks at a community level (Flint, Michigan), in healthcare facilities (such as the Quincy, Illinois veterans home), and due to cooling towers (New York City) have again catapulted Legionella into national headlines. Legionella is now the number one cause of reported waterborne disease outbreaks in the United States, transmitted through contaminated water that is aerosolized and exposing those nearby via inhalation into the respiratory tract.
The bacteria in the genus Legionella occur naturally in water but have optimal growth at warm temperatures. Wherever there are water and pipes eventually one can find Legionella including in many human-made building water systems. However, its exact niche and the factors influencing it to bloom are only now being elucidated. L. pneumophila is the species (among many) most often diagnosed as the cause of Legionnaires’ disease. For every case associated with an outbreak there are nine more sporadic cases. Are these patients exposed in hospitals, from cooling towers, or within residences or commercial buildings such as hotels? Who is responsible for monitoring and controlling the bacteria and the disease? These are complex issues and despite major gains in knowledge about the bacteria, its ecology, its transmission, and Legionnaires’ disease, there remains great uncertainty about how to control Legionella in water systems.
The National Academies of Sciences, Engineering, and Medicine were asked by the U.S. Centers for Disease Control and Prevention (CDC), the U.S. Department of Veterans Affairs (DVA), the U.S. Environmental Protection Agency (EPA), and the Alfred P. Sloan Foundation to address the state of the science with regard to Legionella including its ecology, disease diagnosis, amplification within water systems, quantification, prevention and control, policy and guidance, and all associated research needs.
This study was established under the auspices of the Water Science and Technology Board (WSTB) of the National Academies. The WSTB convened a Committee to address the management of Legionella in water systems that included 13 individuals with various backgrounds and expertise in Legionella. Over the course of two years, the Committee
conducted a scientific literature review on the state of the science, covering the biology, taxonomy, and ecology of the bacteria; outbreaks and disease surveillance; environmental data from all types of building water systems; control methods; and rules and guidelines for addressing Legionella contamination. It conducted some original data analyses, and formulated conclusions and recommendations meant to improve management of Legionella contamination of water systems and consequently better control Legionnaires’ disease in the United States.
The Committee recognizes that Legionella is only one of a number of pathogens found in water distribution systems and in building premise plumbing. Some of these other pathogens may be as serious as Legionella, such as Mycobacterium avium (and other nontuberculous mycobacteria). The control of Legionella may have unintended consequences on these other organisms, as discussed briefly in Chapter 4. However, it was not the purpose of this Report to consider organisms beyond Legionella.
During its six committee meetings, the Committee heard from experts involved in characterizing, monitoring, and remediating Legionella as well as from those knowledgeable about Legionella control policies from Australia, Canada, and Europe. I would like to thank the following individuals for giving formal presentations to the Committee including Sam Posner, Laura Cooley, Jason Kunz, and Brian Raphael, CDC; Shantini Gamage, Gary Roselle, and Oleh Kowalskyj, DVA; Eric Burneson, EPA; Paula Olsiewski, Sloan Foundation; Janet Stout, Special Pathogens Lab; Tim Keane, Legionella Risk Management, Inc.; Jennifer Clancy, Environmental Science, Policy, and Research Institute (ESPRI); Christopher Crawford, New York City Department of Health and Mental Hygiene; Jessica Evans, National Sanitation Foundation International; David Krause, Forensic Analytical Consulting Services; Alvin Bartels, National Institute for Public Health and the Environment, The Netherlands; David Cunliffe, SA Health, Australia; Martin Exner, University of Bonn, Germany; John V. Lee, Leegionella Ltd., United Kingdom; and Gary Klein, Gary Klein and Associates. The Committee also thanks the many individuals who spoke during open-mic sessions or submitted written comments to the Committee during the course of the study.
This Consensus Study Report was reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise. The purpose of this independent review is to provide candid and critical comments that will assist the National Academies of Sciences, Engineering, and Medicine in making each published report as sound as possible and to ensure that it meets the institutional standards for quality, objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process.
We thank the following individuals for their review of this report: Zia Bukhari, American Water; Anne Camper, Montana State University; Elizabeth Casman, Carnegie Mellon University; Jennifer Clancy, ESPRI; David Fisman, University of Toronto; Marian Heyman, Connecticut Department of Public Health; Sophie Jarraud, Lyon Medical School; Richard Miller, University of Louisville; Norman Pace, University of Colorado; and Caitlin Proctor, Purdue University.
Although the reviewers listed above provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations of this report nor did they see the final draft before its release. The review of this report was overseen by Rhodes Trussell, Trussell Technologies, Inc., and Glen Daigger, One Water Solutions, LLC. They were responsible for making certain that an independent examination of this report was carried out in accordance with the standards of the National Academies and that all review comments were carefully considered. Responsibility for the final content rests entirely with the authoring committee and the National Academies.
Joan B. Rose, Chair
Committee on Management of Legionella in Water Systems