Legionella: Out of Sight, Not Out of Mind

Outbreaks of Legionnaires’ Disease often make headline news and result in damage to reputation, loss of business, and costly litigation. Within the past year, news coverage of Legionnaires’ Disease outbreaks has implicated major brand hotels in Wisconsin, Illinois, and Atlanta; a suburban Chicago hospital and a hospital in Columbus, Ohio; senior living centers in Illinois, Connecticut, Utah, and New Jersey; and a hot tub display at a North Carolina State Fair. Legionella Outbreaks, Special Pathogens Laboratory, https://bit.ly/2VgjAuz. Exposure claims and sensationalized media coverage are often brought absent and in advance of conclusive clinical and environmental evidence linking an individual’s disease with an alleged site of exposure. Claims often proceed based solely on circumstantial evidence such as anecdotal travel and locational history for the two- through ten-day time window preceding the onset of symptoms (incubation period).

Legionella in the Environment

Legionella is a genus of rod-shaped (bacilli) bacteria with at least 58 known species, of which 20 species are known to have the potential of causing disease in humans. Legionella Species, Special Pathogens Laboratory, https://bit.ly/2JRJzDt.. One species, Legionella pneumophila, is thought to be responsible for 80-90 percent of respiratory infections that are caused by Legionella bacteria. Razina Khayat, et al., Epidemiological Trends of Reported Legionnaires’ Disease in Houston, Texas, 2014-2017, 11 Online J. of Pub. Health Informatics (2019).

In nature, Legionella bacteria are found in freshwater aquatic environments worldwide at relatively low concentrations that typically do not present a health concern. When a water supply system containing naturally present Legionella bacteria enters a building, the way the water is stored, heated, and circulated can sometimes create optimal habitat conditions for the Legionella bacteria to multiply. Legionnaires Disease Cause and Spread, U.S. Department of Health and Human Services Centers for Disease Control and Prevention, https://bit.ly/2Rqh6ZE.

There are several elements known to promote the growth of Legionella bacteria including excessive water age, biofilm, water temperatures between 77°F - 108°F, dead legs in water pipes caused by no flow or low flow conditions, insufficient disinfection, inadequate corrosion control, or cross-connections between potable and non-potable water systems. Any of these elements, either alone or combined, can lead to Legionella colonizing a building water system, increasing the bacteria counts to thousands of times above the level in the incoming water supply, and potentially exposing people to Legionella in the water. Just the Facts: Legionella and Water Supply Systems, Plumbing Manufacturers International, https://bit.ly/2VfRaRn.

Disease Types and Transmission

There are two types of diseases attributed to Legionella bacteria: Pontiac Fever and Legionnaires’ Disease. Collectively, these two adverse health outcomes are termed Legionellosis. Pontiac Fever is a mild flu-like illness that is non-lethal, is often medically undiagnosed, and resolves without antibiotic therapy. Legionnaires’ Disease is a more severe form of Legionellosis, which results in pneumonia and is potentially fatal. The CDC reports that Legionnaires’ Disease kills 25 percent of those who acquired it from a health care facility, compared to a mortality rate of 10 percent for the general population. Legionnaires Disease Diagnosis and Treatment, U.S. Department of Health and Human Services Centers for Disease Control and Prevention, https://bit.ly/2JRL3xx. From 2000 to 2017, the reported incidence of Legionnaires’ disease has increased more than five-fold. National Academies of Sciences, Engineering, and Medicine, Management of Legionella in Water Systems (The National Academies Press. 2019) https://bit.ly/34ntWgi.

Legionnaires’ Disease is usually acquired by inhaling aerosol droplets or mist containing Legionella bacteria into the lungs. Outbreaks of Legionnaires’ Disease are often associated with complex building water systems with the most likely points of exposure being showerheads, sink faucets, cooling towers, ice machines, hot tubs, decorative fountains, water features, and humidifiers. Infection can also occur by aspiration of contaminated water or ice, particularly in hospitals or long-term care facilities, as well as from at-home birthing pools. World Health Organization, Legionellosis, https://bit.ly/39XjRYs. A common misconception is that any air conditioning system can present a concern for Legionella exposure. Refrigerant-based air-conditioning systems commonly found in modern residential and vehicle applications do not present a risk for Legionella exposure as they do not use water. Only cooling systems that use water for heat rejection purposes, such as cooling towers and swamp coolers, present a concern for exposure to aerosol mist potentially contaminated with Legionella bacteria. Legionnaires Disease Cause and Spread, U.S. Department of Health and Human Services Centers for Disease Control and Prevention, https://bit.ly/34mroPF

Not every individual exposed to Legionella bacteria develops Legionnaires’ Disease. Individuals at increased risk of developing Legionnaires’ Disease include adults over 50 years old, current or former smokers, and people with a weakened immune system or chronic disease. Id.

Regulations and Standards

A collection of regulations and standards exist to guide in developing site-specific best practices for reducing the risk of building-related Legionellosis. Notable guidance published by ASHRAE® and approved by ANSI in 2015, and recently updated in 2018 is found in ASHRAE Standard 188-2018, “Legionellosis: Risk Management for Building Water Systems.” In June 2017, the CDC published an online toolkit, which provides a simplified seven-step process based on key elements of the ASHRAE standard which include:

1. Establish a water management team.
2. Describe the building/facility water systems using both text and flow diagrams.
3. Identify suspect areas where Legionella could grow and spread.
4. Decide where control measures should be applied and how to monitor the control measures.
5. Establish ways to intervene when control limits are not met.
6. Make sure the program is running as designed and is effective.
7. Document and communicate all the activities.

Developing a Water Management Program to Reduce Legionella Growth & Spread in Buildings, U.S. Department of Health and Human Services Centers for Disease Control and Prevention, https://bit.ly/3a1202R.

In June 2017, the Centers for Medicare and Medicaid Services (CMS) issued a memorandum requiring certain facility types, such as hospitals, critical access hospitals, and long-term care facilities, to develop water management programs aimed at reducing the risk of Legionellosis attributable to building water systems. Director, Quality, Safety, and Oversight Group, Requirement to Reduce Legionella Risk in Healthcare Facility Water Systems to Prevent Cases and Outbreaks of Legionnaires’ Disease (LD), U.S. Department of Health and Human Services Center for Medicare and Medicaid Services, https://go.cms.gov/2y4sa7A.

In 2019, the National Academies of Sciences, Engineering, and Medicine released a consensus study report titled “Management of Legionella in Water Systems” which addresses the state of the science about Legionella including its ecology, disease diagnosis, amplification within water systems, quantification, prevention and control, policy and guidance, and associated research needs. The consensus report provides numerous recommendations including the importance of expanding training and education, particularly for those designing water systems, overseeing municipal water supplies, developing and implementing plumbing codes, maintaining water operations and premise plumbing, and those in government who are responsible for the safety of buildings, cooling towers, and the potable water supply. Furthermore, the report recommends expanding the CMS memorandum to require monitoring for Legionella in environmental water samples, registering and monitoring cooling towers, requiring water management plans in all public buildings including hotels, businesses, schools, apartments, and government buildings, and requiring a temperature of at least 140°F at hot-water heaters with temperatures of at least 131°F maintained to delivery at distal locations immediately before points-of-use. It is important to note that the delivery temperature of water at points-of-use is often regulated by plumbing code or in healthcare settings to prevent scalding. This may require tempering of the hot-water nearby a point-of-use by using mixing valves or at the point-of-use with a tempered fixture. Many older buildings lack the plumbing configuration or modern fixtures which provide for tempering near the point-of-use, thus contributing to the risk of building-related Legionellosis by heating, storing, and delivering water at lower temperatures that are targeted to achieve a compliant temperature at points-of-use. Management of Legionella in Water Systems, supra.(.

Managing Risks

Increased attention and research on Legionella hazards require risk managers to reconsider water management practices for their facility. Considering the ongoing increase in reported cases of Legionellosis, and the accompanying media attention, reputational damage, and potential litigation, risk managers for facilities with at-risk individuals should strongly consider voluntarily adopting current best practices, including routine water testing to validate the efficacy of implemented programs. Risk managers with less at-risk populations, but with centralized domestic hot water systems, pools, and spas, decorative water features, or cooling towers, should also consider implementing a water management program following best-practices guidelines.