June 18, 2024

Waterborne Threats: Legionella Testing Strategies for Public Safety

Legionella Testing: Understanding the Importance of Bacteria Detection

Legionella bacteria are commonly found in natural and man-made water systems. While Legionella are generally harmless, they can cause a serious type of pneumonia called Legionnaires’ disease in people who are at increased risk. Proper Legionella testing and prevention methods help protect public health. This article explores why Legionella testing is important, methods for testing, and recommendations for prevention.

What is Legionella and Legionnaires’ Disease?

Legionella bacteria normally inhabit freshwater environments but can proliferate and spread in human-made building water systems like cooling towers, showers, fountains, and plumbing. People can get sick when they breathe in contaminated water droplets containing Legionella bacteria in aerosol form.

Legionnaires’ disease is a severe pneumonia that can be fatal in about 10% to 30% of cases. It usually affects the elderly, smokers, heavy drinkers, diabetics or people with chronic lung diseases or weakened immune systems. Symptoms of Legionnaires’ disease include fever, cough, shortness of breath, muscle aches, and headaches. Prompt diagnosis and treatment with antibiotics are important to recovery. An estimated 8,000-18,000 people are hospitalized with Legionnaires’ disease in the United States each year.

Testing Methods and Guidelines

There are multiple testing methods for detecting Legionella in water systems depending on the application and need for quantitative or qualitative results. Culture testing remains the gold standard, though newer molecular tests like polymerase chain reaction (PCR) provide faster results.

The Centers for Disease Control and Prevention (CDC) recommends routine testing for hospitals, nursing homes, cooling towers, and other certain building types where immunocompromised people may be exposed to contaminated aerosols. Periodic testing ensures building water systems remain free of Legionella colonization and confirms disinfection methods are working properly to control levels. Compliance with CDC testing guidelines helps prevent disease outbreaks linked to the built environment.

Routine Testing Benefits Public Health

Proactive Legionella monitoring through routine testing allows facilities to quickly identify potential problems before an outbreak occurs. If Legionella is detected, facilities can address the issue right away through remediation of the water system. This includes draining tanks, hyperchlorination or other disinfection, and system repairs or modifications to inhibit future bacterial growth.

Catching Legionella contamination early through routine testing protects both building occupants and the surrounding community. Large disease clusters are more likely when problems go undiscovered for long periods of time. Rapid remediation means fewer people are exposed to risk. Additionally, routine testing data creates an evidence trail to demonstrate due diligence if an outbreak does occur despite best prevention efforts.

Testing After Remediation Ensures Safety

When Legionella is found through testing, facilities undergo remedial processes to eliminate the bacteria from plumbing networks. However, the treatment itself can temporarily increase risk by disturbing bacterial reservoirs and generating aerosolized Legionella. Post-remediation testing ensures disinfection was successful before allowing public access again.

Negative results from post-treatment samples, taken in accordance with CDC guidelines, prove the water network is Legionella-free and any risks to public health have been resolved. It provides quality assurance the system is safe for normal operation and occupant exposure is minimized. Without verifying removal through testing, the effectiveness of decontamination cannot be confirmed.

Legionella Prevention Through System Maintenance

Routine maintenance and monitored temperatures in building water networks also help inhibit Legionella growth and protect public health long-term. Cooling towers should maintain temperatures below 68°F, while hot water should be above 140°F to discourage bacterial colonization. Stagnant sections of plumbing prone to microbial growth should be flushed periodically.

Scale, sediment and biofilms Harbor Legionella and promote colonies, so maintaining clean systems through regular descaling, disinfection and hydraulic evaluation reduces breeding grounds. Proper design, operation and care are as important to prevention as testing to catch issues before an outbreak occurs. A comprehensive Legionella control plan encompassing testing, treatment and maintenance safeguards communities.


Legionella testing plays a vital role in preventing disease by uncovering contamination that could put building occupants and the public at serious risk. Used in conjunction with recommended prevention methods, routine monitoring and rapid remediation create multiple safety barriers against Legionnaires’ disease. Compliance with CDC guidelines demonstrates due diligence and helps strengthen community health protections against this often-fatal pneumonia. Proactive Legionella control through regular testing and maintenance should remain a priority for facilities serving vulnerable populations.


  1. Source: Coherent Market Insights, Public sources, Desk research
  2. We have leveraged AI tools to mine information and compile it