Legionnaires’ disease bacteria illustration. Close-up view of bacteria under a microscope. Created by AI.

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Introduction

Legionnaire’s Disease (LD) is a potentially life-threatening pneumonia caused by the Legionella pneumophila bacteria. The infection is also known as Legionnaires’ pneumonia, legionellosis, or legion fever. The same microbe causes a milder, nonpneumonic infection called Pontiac fever or nonpneumonic legionellosis.^1,2

The disease was first identified after a July 1976 American Legion convention at the Bellevue-Stratford Hotel in Philadelphia, when over 200 attendees developed pneumonia and 34 died. The CDC launched an investigation, which led to the identification of Legionella pneumophila in the hotel’s air system.²

LD is spread by inhalation of aerosolized droplets of water that are contaminated by L. pneumophilia. Sources include air conditioning systems, showers, nebulizers, hot tubs, and decorative water features. Infection requires the inhalation or aspiration of these droplets into the lungs.

People at increased risk of infection are adults over 50 years, current or former smokers, people with a weakened immune system, diabetics, and people with chronic lung or kidney diseases, characteristics that describe most residents of long-term care facilities. The average death rate in health care-associated cases is around 25%.^1,3 Therefore, long-term care facilities must have adequate and effective prevention and control measures for LD for the safety of their residents.

In response to an increase in cases, most of them occurring in long-term care facilities, the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) developed an industry standard for the development and implementation of water management programs in 2015. CDC and its partners developed a toolkit for the implementation of the ASHRAE standard in 2016, and in 2017, the Centers for Medicare & Medicaid Services (CMS) released a requirement for facilities to prevent Legionella infections by developing water management policies and procedures.⁴

Many resources and toolkits are available to aid the development of a water management plan:

• Water Management Program Toolkit, CDC | PDF
• Water Management Program Template, 2018, NEHA | PDF
• Legionella Literature Review, EPA | Webpage
• Standard 188 – Legionellosis Risk Management, ASHRAE | Webpage (requires purchase)
• Water Management in Health Care Facilities, ASHE | Webpage

Components of an effective Water Management Program (WMP)

Team

The first piece of an effective water management program (WMP) is the development of a team. Infection preventionists are proficient at many things; however, we must engage other departments and show how infection prevention is everyone’s business. This team should be granted authority to intervene in any water-related issues that arise in the facility.

A water management team should include the following, when applicable: Infection prevention, facility or building management, maintenance, environmental services (EVS), safety officer, accreditation, risk and quality management, equipment suppliers, consultants (eg, water treatment and testing), industrial hygienist, microbiologist, and public health (state or local).

The team will develop, monitor, and document program requirements, performance metrics, and report to committees like the infection prevention and control committee and quality and performance improvement (QAPI). The team should meet at least annually to review and update the plan, but more frequently in response to incidents.^5,6,7

It is common to experience tension over the ownership of the WMP. It is infection-related, but most of the work is done by the maintenance or the environment of care team. Any of these departments' team members may lead the water management team. The responsibility does not lie with one department. An effective WMP requires collaboration between IP and various departments within the Environment of Care (ie, EVS, maintenance, building managers, etc.).

Risk Assessment

The WMP team must start by developing a description of the facility’s entire water system from initial supply, distribution, and heating, to the sewer. The description must include all buildings and equipment that aerosolize water droplets. This can be accomplished by prose, tables, or diagrams.

We know that L pneumophilia thrives in water temperature ranges of 77°F to 113°F (25°C to 45°C); therefore, the next step is to identify where those temperatures can be attained, where the microbes can grow. Other hazards include water stagnation, aerosolization, and the absence of disinfection.^1,5,6,7

The completion of the risk assessment may require input from your locality’s water department. They are also a good source of water quality reports, which can be helpful when setting control limits.

Control Measures

The growth and spread of L pneumophilia occur when water is stagnant, eg, emergency water, vacant rooms, or dead legs (“Dead legs” refers to a section of pipe where water becomes stagnant because it leads to an outlet that is unused or rarely used.). Such places will allow water to cool down and allow for the degradation of disinfectants. These conditions can be controlled by disinfection, cleaning, and heating. This step also includes identifying where control measures are applied and the relevant control limits.

Various chemicals disinfect water. Measuring the disinfectant residual at the supply point and at the fixtures is an available control measure. The concentration of residual disinfectants is affected by the length of time water spends in transit (from supply to fixture), temperature, amount of sediment, and biofilm. Disinfectants work best within specific pH ranges, so this is another control limit that must be set and monitored. The acceptable ranges for both metrics depend on the fixture and the disinfectant in use.

Water must be stored and circulated colder than 77°F (25°C) and hotter than 120°F (49°C) in the absence of local and state regulations. Other control measures include Adenosine triphosphate (ATP) Testing and microbial testing. Many of these have published guidelines and regulations. The choice you make depends on access and cost.^5,6,7

Monitoring

The team must determine how frequently to monitor their selected control measures. Monitoring must occur at the supply points and at the identified high-risk fixtures. Some easy monitoring points are emergency water lines and infrequently used sinks. Some critical monitoring points are water sources for nebulizers, cooling towers, and water features. If resources are limited, monitoring points can be grouped and tested in a rotation. The monitoring plan, locations, frequency, and control limits must be stated in the WMP.

LD is a nationally notifiable disease in the United States, so it must be included in the surveillance plan of every infection prevention and control program. Part of WMP monitoring is surveillance for health care-associated cases of LD.

Training

The team must provide training to staff on the importance of the WMP and how to reduce the risk of LD in residents and staff. A frequently overlooked aspect of staff education is that adherence to many safety measures reduces the risk of occupational exposures.

Frontline staff are the best people to identify rarely used water fixtures. It is reasonable to schedule the flushing of those fixtures by staff to reduce the risk of disinfectant degradation. Training must also include how to report concerns with water quality. We are at a time when burnout is rife, and staff engagement is low. Note that there is greater buy-in when staff see how a policy affects their own safety.⁸

Verification

Regularly verify that the WMP is working as intended and that you are meeting the set goals. This can be done using inspection checklists and running water quality drills. The team must report to oversight committees, as dictated by facility policies. The infection prevention and control committee, the environment of care committee, and QAPI are reasonable groups to report to if other guidance is lacking.

Conclusion

The task of meeting the WMP requirement is daunting if approached from a siloed perspective. This is an initiative that requires multidisciplinary expertise and engagement. To make it that much easier, many toolkits are available to aid the implementation of this resident and staff safety program.

References

1. Government of Canada. Legionella pneumophila: Infectious substances pathogen safety data sheets. Government of Canada. December 18, 2023. Accessed September 9, 2025. https://www.canada.ca/en/public-health/services/laboratory-biosafety-biosecurity/pathogen-safety-data-sheets-risk-assessment/legionella-pneumophila.html
2. CDC. About Legionnaires' Disease. Legionella (Legionnaires' Disease and Pontiac Fever). August 06, 2025. Accessed September 9, 2025. https://www.cdc.gov/legionella/about/#cdc_disease_basics_case-history.
3. CDC. How Legionella Affects Building Water Systems and People. Legionella (Legionnaires' Disease and Pontiac Fever). June 09, 2025. Accessed September 9, 2025. https://www.cdc.gov/legionella/communication-resources/infographic.html?CDC_AAref_Val=https://www.cdc.gov/legionella/infographics/legionella-affects-water-systems.html.
4. CMS. Policy & Memos to States and CMS Locations. CMS. June 02, 2017. AccessedSeptember 9, 2025. https://www.cms.gov/medicare/provider-enrollment-and-certification/surveycertificationgeninfo/downloads/survey-and-cert-letter-17-30.pdf.
5. CDC. Toolkit: Developing a Legionella Water Management Program. Controlling Legionella. March 15, 2024. Accessed September 9, 2025. https://www.cdc.gov/control-legionella/php/toolkit/wmp-toolkit.html.
6. Gulledge HP, Booth R, Gaetano J, Stemke O, Flannery J. Water Management in Health Care Facilities, Second Edition. Chicago 2025.
7. NEHA. Legionella. NEHA. 2018. Accessed September 9, 2025. https://www.neha.org/Images/resources/Water%20Management%20Program%20Template_June2019.pdf.
8. Rindal KDC. A Three-Tiered Approach to Securing Buy-In for Safety Initiatives. Incident Prevention. December 2024. Accessed September 9, 2025. https://incident-prevention.com/blog/a-three-tiered-approach-to-securing-buy-in-for-safety-initiatives/.
9. CDC. Overview of Water Management Programs. Controlling Legionella. March 05, 2024. Accessed September 9, 2025. https://www.cdc.gov/control-legionella/php/wmp/index.html.