Contributed by Kelsey Bonhivert, Compliance Specialist, PPM Consultants
Introduction
Recent outbreaks of Legionnaires’ disease are bringing national attention to the disease, and, on a related front, importance of appropriately managed water systems. In late July through August 2025, a Harlem neighborhood faced a deadly Legionnaires’ disease outbreak that left more than 100 people sick and seven dead. Investigators traced the source to contaminated cooling towers atop Harlem Hospital and a nearby construction site. Another outbreak occurring In Iowa since August 2025, is under investigation and suspected to stem from contaminated cooling towers, leading to over 50 cases of Legionnaires’ disease, including one death.
Legionnaires’ disease is a severe type of pneumonia caused by over 60 different Legionella species, with the majority of identified cases linked to Legionella pneumophila. These bacteria thrive in warm water and spread when contaminated droplets become mist or fine spray that can be inhaled. While cooling towers often draw headlines, the risk extends far beyond these systems.
While outbreaks linked to cooling towers at hospitals, nursing homes, and large residential buildings often draw headlines, the risk extends far beyond these systems. People don’t need direct contact with contaminated water— simply walking nearby aerosolized, contaminated water can be enough to cause illness. These events can serve as a reminder that Legionella is not just a public health issue — it is a workplace safety concern, including industrial and manufacturing environments.
Examples of Industrial Exposure
Documented cases from industrial facilities demonstrate that industrial facilities are not immune to Legionella risks. Overlooked equipment and water systems in manufacturing environments can create the same conditions for outbreaks:
- Ontario, Canada (2025): An outbreak linked to cooling towers at a food processing facility was confirmed through testing of both patient samples and the towers themselves. Initially declared over on August 6, 2025, the outbreak was redeclared on August 26 after new cases emerged. To date, at least 94 cases have been reported, including 86 hospitalizations and four deaths. A similar outbreak in the same region the year before was also suspected to be tied to cooling towers, though the specific source was never identified.
- South Carolina, USA (2022): An outbreak at a manufacturing facility led to 34 employee cases, including 15 hospitalizations and two deaths. Investigators traced the source to high-pressure water jet cutters and a floor scrubber. Both types of equipment can retain water under conditions favorable to bacterial growth and can release contaminated droplets into the air, creating opportunities for inhalation exposure.
- New York, USA (2009–2011): Over a three-year period, four employees developed Legionnaires’ disease while working at an automobile and scrap metal shredding facility. The shredding operation was cooled and lubricated with water, creating conditions for Legionella growth. A NIOSH case study found that workers were exposed when dust, mist, and vapor generated by the operations, and when performed routine jobs tasks in areas with standing water — both of which increased the chances for contaminated water to become airborne.
Challenges in Identification
Legionnaires’ disease is chronically underdiagnosed and underreported, leaving significant data gaps. Because it often looks like the flu or other pneumonias, many infections are never tested for Legionella. Even confirmed cases may not trigger full investigations if resources are limited. The result is that both individual cases and outbreaks frequently go unrecognized, making it extremely difficult to measure the true burden of the disease in industrial and manufacturing facilities.
Tracing cases back to a source is equally challenging. People who become sick may not share a clear exposure, and with an incubation period of up to two weeks, infections often appear sporadic rather than connected. Privacy and legal concerns add another layer of complexity: health agencies and companies are often reluctant to name specific facilities, and in industrial settings many cases are privately handled through the workers’ compensation system, keeping the information out of public view.
How to Evaluate Your Facility’s Risk
The CDC publishes guidance, toolkits, and training resources to help facilities across different sectors identify and mitigate risk. An essential step in evaluating your facility is by developing a Water Management Program (WMP), which will identify potentially hazardous conditions that could harbor the growth of Legionella, and outline control measures to minimize health impacts.
The following sources for Legionella growth are examples of water usage that are common in industrial and manufacturing environments:
- Secondary water systems that collect, store, or use recycled water, gray water, rainwater, etc.
- Water storage for high-demand use
- Fire suppression systems
- Safety showers and eyewash stations
- Evaporative air coolers
- Comfort misters
- Pressure washing equipment
- Lubrications and Cooling systems for machines and metal working
- Ice machines
- Water heaters and reservoirs containing water between 68–113°F
Additionally, the specific case examples discussed earlier highlight the fact that Legionella growth and spread can stem from other water sources. Without control, Legionella can grow in almost any system or equipment containing nonsterile water at favorable temperatures. For potential sources of Legionella that are not explicitly identified in the CDC’s toolkits, further evaluation should be conducted.
A WMP’s effectiveness depends on being actively maintained, reviewed, and updated to keep pace with changes in equipment, operations, and risk. Routine testing is often a critical component, serving to verify that control practices are working as intended. Facilities should also confirm with their local or regional health agencies whether testing is required within their jurisdiction.
When it comes to Legionella, there is no safe threshold — any presence poses a potential risk. A comprehensive WMP should clearly outline the frequency of testing, the locations to be sampled, the methods to be used, and a progressive set of corrective actions if Legionella is detected. Rapid tests conducted on site can be valuable for early screening and warning, but full laboratory culture testing remains the gold standard, providing definitive results on bacterial strain and growth trends. Health agencies, accredited laboratories, or consultants can assist facilities in selecting appropriate test methods for the specific risks of their operations.
If your facility has not recently conducted a screening for Legionella risk, it may be time to refresh awareness. Legionnaires’ disease is a workplace issue that manufacturers cannot afford to ignore, as overlooked water systems in industrial settings can harbor Legionella and spread illness without warning. With many cases going unrecognized and data remaining limited, the true scale of the problem is likely larger than it appears. Prevention is always easier than response. By staying aware of the risks and taking care to implement strong water management practices, facilities can protect their workers from the hidden dangers of Legionnaires’ Disease. If your facility is in need of a WMP or you would like to discuss this topic, please feel free to contact me at kelsey.bonhivert@ppmco.com.