Should You Test for Legionella?

According to the Centers for Disease Control (CDC), Legionnaires’ disease is on the rise in the United States. In 2000, roughly 1000 cases were reported. That number ballooned to 10,000 cases in 2018, the last year for which data is available. The CDC issued a 2021 report on waterborne diseases, but this report only looks at cases of Legionellosis associated with an outbreak. Most cases of waterborne diseases, including Legionnaires’ disease, are sporadic, i.e., not epidemiologically linked to other cases by time, location of exposure to water, and type of illness.

No matter how you calculate cases, the figures may underrepresent the actual number of cases, as the disease is likely underdiagnosed. After all, Legionnaires’ disease is a respiratory illness, and there are plenty of those to go around.

In this post, we’ll explore Legionella, the bacteria that causes Legionnaires’ disease, what conditions facilitate its growth, and which industries should consider a proactive approach to Legionella testing.

What is Legionella?

Legionella is a bacteria found naturally in freshwater environments, such as rivers and lakes. Typically, Legionella only becomes a problem when it infiltrates constructed water systems such as plumbing networks, hot water tanks, cooling towers, and hot tubs. This colonization can occur when water containing Legionella, often in undetectable numbers, enters the building.

It takes the right conditions for Legionella to proliferate and cause an outbreak. Conditions that promote the growth of Legionella include:

• Temperatures between 68-113°F (20-45°C)
• Stagnant water with little flow or circulation
• The presence of biofilm, other microbes, scale, and organic matter
• Corrosion or inefficient maintenance of water system components

Human exposure to Legionella mainly occurs through inhaling aerosolized water droplets containing the bacteria. Even then, healthy individuals may never know they’ve been exposed as the very young, very old, and immunocompromised are more likely to fall ill.

There are currently two recognized diseases caused by Legionella. The less dangerous of the two, Pontiac fever is a mild, flu-like illness that usually does not develop into pneumonia. Symptoms include fever, headache, and muscle aches. Pontiac fever often resolves on its own without causing long-term complications.

The better-known Legionnaires' disease is a severe form of pneumonia accompanied by symptoms such as cough, shortness of breath, fever, muscle aches, and headaches. Legionnaires’ disease can lead to severe respiratory complications and even death if not treated promptly.

What Types of Businesses Should Be Testing for Legionella?

Certain industries should prioritize Legionella testing due to the potential risk associated with exposure and the nature of their water systems. First, let’s cover the top three named categories according to the CDC.

Healthcare Facilities – When exposed to Legionella, individuals with a healthy immune system can often fight off the bacteria and avoid becoming ill. However, like many other illnesses, individuals with weakened immune systems are much more susceptible. Again, looking at CDC data from 2018, 18.1% of Legionnaires’ disease cases and 9.8% of deaths from Legionnaires’ disease were suspected to have originated through exposure in the healthcare system. In 2021, the CDC stated that routine testing for Legionella is particularly beneficial for healthcare facilities.

A water management plan in healthcare isn’t just a good idea. It’s often required by law. The Centers for Medicare & Medicaid Services (CMS) require healthcare facilities to develop one designed to reduce the risk of Legionella and other pathogens in their water systems. CMS recommends healthcare facilities consider the ASHRAE 188 standard. Similarly, The Joint Commission, an important accrediting body for hospitals, requires hospitals to have water management plans and points towards ASHRAE 188 for guidance.

Assisted/Senior Living Facilities – It’s worth noting that the healthcare origination data published by the CDC does not include senior or assisted living facilities. In 2018, only 3.7% of cases were suspected to have originated in an assisted living facility. However, these cases account for 9.2% of deaths from Legionnaires’ disease, almost as many as originated in the healthcare system. As these facilities often accept Medicare and Medicaid residents, they are typically subject to the ASHRAE 188 standard.

Hospitality Industry – Travel was the second highest exposure category in the CDC data at 14.6% of confirmed cases and 2.7% of deaths. Hotels, motels, and resorts often have large and complex water systems, which can become sources of Legionella contamination.

Remember, the ideal temperature for Legionella growth is between 68-113°F (20-45°C). Hot tub temperatures vary but generally range between 100 and 104°F. Heated pools are cooler, but with temperatures usually set in the mid-80s, they can easily become fertile breeding grounds for Legionella. Add in inadequately maintained systems and aerosolized water droplets from a poolside waterfall or fountain, and you have ideal conditions for an outbreak.

We’ve covered the top three CDC-named sources of outbreaks, but we still have over 60% of cases and almost 6% of deaths from Legionnaires’ disease unaccounted for. We can look to the conditions that support the growth of Legionella to identify potential hot spots. Here are a few other potential sources of exposure:

Data Centers – Data centers are known for generating significant amounts of heat due to the vast array of complex computer systems typically housed within these facilities. Cooling towers are used to dissipate this unwanted heat into the atmosphere. Open-circuit cooling towers are the most common type. These systems use water open to the air to dissipate heat. If these towers are not properly cleaned, disinfected, and maintained, they can become an ideal breeding ground for Legionella.

Public Institutions – Schools, universities, and government buildings water systems are also susceptible to Legionella growth without appropriate maintenance. For instance, many larger institutions still operate their own on-site data centers and use water evaporation systems to cool them. They may also operate health and wellness facilities that provide access to public showers, heated pools, and hot tubs. Legionella can also be dispersed through improperly maintained air conditioning systems.

At least one state, Virginia, requires public schools to develop water management programs and test for Legionella. In addition, the General Services Administration (GSA) released an order in February of 2023, requiring Legionella testing in federally owned large buildings, childcare centers, and healthcare units.

Industrial Facilities and Commercial Buildings – Cooling towers are used extensively in industry to disperse excess heat. For instance, oil and petroleum refineries generate a significant amount of heat, and cooling towers are used to keep the temperature under control. Plastics manufacturing and processing often requires heat, necessitating the need for cooling systems. The food and beverage and pharmaceutical industries frequently use cooling systems to maintain the optimal temperature conditions vital to product safety and quality.

Furthermore, commercial air conditioning systems have all the elements that favor Legionella growth, including warm temperatures, water stagnation, and sometimes, improper maintenance. Inspection, diagnosis, and repair of cooling towers and air conditioners is vital, with particular attention paid to the proper management of condensate drainage systems. The Cooling Tower Institute Guideline 159 has specific recommendations for Legionella testing and water management of cooling towers.

Don’t Wait Until You Know You Have a Problem

Unfortunately, unless they’re required by law to have a water management plan, too many businesses and institutions wait until there’s a suspected outbreak to test their water systems. We should note that the ASHRAE 188 standard used by so many across industries does not mandate testing for Legionella and other waterborne pathogens. However, reactive testing for Legionella can be significantly more costly than proactively performing routine testing. Besides the direct costs related to public health investigations, laboratory testing, and immediate remediation efforts after an outbreak, there may be substantial indirect expenses such as lawsuits, damage to company reputation, and loss of business.

Proactive testing can help validate a water management plan and allow the organization time to budget and plan for necessary system modifications, improvements, and routine maintenance in a more controlled, predictable, and efficient manner. Moreover, regular testing and upkeep for Legionella bacteria prevention are considered standard practice for maintaining a safe environment and can reduce potential liability.

Pace® can help you assess your risk profile and develop a plan for routine testing that meets your regulatory requirements and reduces exposure. Contact us today to learn more.