Management of Legionella in Water Systems (2020) / Chapter Skim
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1 Introduction
1 Introduction
Pages 11-30
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From page 11... ...
Of the nearly 2,000 conference attendees, 182 people developed clinical disease and 29 died from their illness. This large outbreak generated national alarm, as public health experts, laboratory scientists, and clinicians raced to define the pathogen (Winn, 1988)
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. In the first few years after the outbreak, scientists identified the pathogen, procedures critical for laboratory isolation, common environmental sites of exposure (e.g., air conditioning units, cooling towers, potable water)
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pneumophila strain Outbreak of pneumonia at an American Legionella linked to potable Outbreak in Bronx, NY, related identified by Bozeman and Legion Conference Bellevue-Stratford Hotel in 2004 to cooling towers.21 Led to water12 colleagues2 Philadelphia, PA, and designation of disease L pneumophila genome cooling tower regulation in at Legionnaires' disease8 sequenced13,14 NYC in 2015 1977 2001 Largest documented 2016 L
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. Legionnaires' disease is acquired by exposure to contaminated aerosols of water generated by manufactured devices such as showerheads and faucets, cooling towers, fountains, hot tubs, and other building water systems.
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. Etiologic shifts from the 1970s to the modern era likely reflect successful efforts mandated by the Safe Drinking Water Act of 1974 to control fecal and enteric bacterial pathogens and parasites (primarily Cryptosporidium spp.
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. FIGURE 1-4 Scatterplot of the burden of selected infectious diseases in disability adjusted life years (DALYs)
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Some of the listed bacteria grow opportunistically in building water systems, but only Legionella causes a reportable illness. Hundreds of organisms associated with waterborne disease are not discussed in detail in this report, including common waterborne pathogens such as Pseudomonas spp., non-tuberculous mycobacteria, Campylobacter spp., Cryptosporidium, and some E
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bacteremia, pneumonia Healthcare- • rimarily occurs in patients with P acquired compromised immune systems • Can grow in building water systems Non-tuberculous bacteremia, pneumonia Both • Primarily Mycobacterium aviummycobacteria intracellulare, but others also reported (Falkinham, 2011) • Can grow in building water systems • High resistance to chlorine Pseudomonas spp.
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systems such as cooling towers and humidifiers; indoor plumbing (called premise plumbing) including outlets such as showerheads and faucets; and spas, hot tubs, and Jacuzzis (collectively called hot tubs in this report)
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Legionella can also contaminate drinking water, either in distribution systems or premise plumbing. In the United States, more than 322 million people are served by 152,000 public drinking water systems with more than 1.2 million miles of water supply mains.
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In 2018, there were estimated to be more than 127 million households in the United States.2 Biofilm and Legionella growth can also be enhanced by water age, which depends on the building type and use, occupancy, and water use. Indeed, the water residing in premise plumbing has a much wider age distribution than the water entering a home from the distribution system (NRC, 2006)
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. In the United States, there are an estimated 9 million swimming pools and 5 million hot tubs.8 Other less common locales in the built environment can provide conditions suitable for biofilm growth, and hence colonization by pathogens such as Legionella and their protozoan hosts.
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Most knowledge regarding Legionnaires' disease comes from investigations of disease outbreaks, in which two or more people are infected at the same time by the same source. Yet, only 4 percent of Legionnaires' disease cases are associated with known outbreaks and are thoroughly investigated (Hicks et al., 2011)
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There is no federal law specifically targeting Legionella. The Surface Water Treatment Rule of the Safe Drinking Water Act only indirectly addresses Legionella via the requirement for maintaining a disinfectant residual in public water supply distribution systems that use surface water sources, and it does not extend to groundwater supplies or to building premise plumbing.
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The need for a quantitative threshold of Legionella concentration above which action must be taken, and the role of quantitative microbial risk assessment, are extensively discussed in this chapter. Chapter 4 considers the many strategies used to control Legionella, including the use of heat, biocides, flow control, aerosol formation prevention, and distal devices, along with their application in several typical built environments.
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2018. Impact of infectious diseases on population health using incidence-based disability-adjusted life years (DALYs)
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Emerging Infectious Diseases 17(3)
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Emerging Infectious Diseases 24(10)
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Emerging Infectious Diseases 22(1)
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Emerging Infectious Diseases 8:37-43.
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