January 27, 2021 zacherlaw 0 Comments

In the United States, incidence of Legionnaires’ disease increased more than six times from 2000 to 2018. Additionally, this number is commonly known to be under reported.

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, and how the country currently handles it. 

Despite numerous reports of common-source outbreaks in the community, through travel or through hospital exposures, and despite improvements in laboratory tools, the vast majority of Legionella cases remain sporadic. Sporadic cases mean that they are community-acquired cases for which the primary exposure source is never identified. This is juxtaposed by outbreaks, meaning two or more people are infected at the same time by the same source.

Most knowledge regarding Legionnaires’ disease comes from investigations of disease outbreaks. However, only 4% of Legionnaires’ disease cases come from known outbreaks and are thoroughly investigated. This leads the researchers at the National Academies of Sciences to determine that the number of outbreaks of Legionnaires’ disease is not accurately represented because of the numerous sporadic cases that go unreported. 

Another common issue with Legionnaires disease cases is doctors fail to diagnose them until it is too late, or it has been successfully treated. When patients present with pneumonia, most physicians choose generic strong antibiotics that adequately treat the disease, so these cases are never counted. Across the world, the actual number of Legionnaires’ disease cases is generally known by the scientific and medical communities to be underreported by as much as eight- to ten-fold.

Among common waterborne bacteria, Legionella is now the most common cause of reported drinking water-associated outbreaks. Diagnosed Legionnaires disease cases are estimated to lead to a cost of approximately $26,000 to $38,000 per admission to the hospital. 

Legionella bacteria naturally reside in many freshwater and soil environments, such as lakes, streams, and sediments, and many different species potentially cause the disease. However, it is the unchecked growth of Legionella in human-made water systems that typically leads to human exposures and causes disease. Humans are exposed to Legionella after inhaling or aspirating contaminated water aerosolized from a variety of sources. 

The last significant problem with Legionella is that it is so inconsistently managed across the United States. For example, healthcare facilities that are part of the Veterans Health Administration system or that receive funding from the Centers for Medicare & Medicaid Services must manage for Legionella contamination, but with varying requirements and oversight. In New York City in the wake of the Bronx Legionnaires’ disease outbreaks in the summer of 2015, regulations to register, monitor, and treat cooling towers were put in place.

Generally, there is an agreement about the levels of Legionella that when detected, require immediate remedial action within a water system. However, there is no consensus on a standard amount to which there is no risk of infection. Increased testing and monitoring of Legionella levels will likely lead to a better understanding of the likelihood for particular water systems to be sources of infection.  [1]

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[1] https://www.nap.edu/catalog/25474/management-of-legionella-in-water-systems

National Academies of Sciences: Management of Legionella in Water Systems: Chapter 1, Part 1 was last modified: March 22nd, 2021 by zacherlaw

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