Legionella Regulations That Work: What Water Labs Need to Know

Outbreaks often trigger sudden, localized responses, such as the enactment of a new law, the issuance of an emergency guideline, or the introduction of a narrowly targeted rule. But do these reactive measures work?

Patsy Root, senior manager of government affairs at IDEXX Water, notes that history suggests otherwise.

"What I've noticed is that there will be an outbreak, there will be public outcry, and then there will be lawmakers who promise their constituents they're going to do something about it," Root said during a recent episode of the podcast Scaling Up!. "The worst time to write a rule is when you're in the middle of a panic."

Her research, "Data and Case Study of Effective Legionella Regulations," compares legislation from North America and Europe, offering a framework for smarter, more effective disease prevention. Below, we'll dive into Root's findings, exploring how aligning policy with pathogen-driven illnesses improves outcomes for public health and the bottom line.

A Patchwork of Legionella Regulations

Legionella regulation in the U.S. is far from uniform. New York City has the most widely recognized law, but similar measures exist across multiple states and agencies.

The U.S. Veterans Health Administration has instituted directives for healthcare facilities, the Centers for Medicare and Medicaid Services mandated water management programs, and New Jersey recently passed its own law. Localized rules also appear in Virginia, Ohio, Michigan, Illinois, and even individual cities such as Garland, Texas, and New Orleans, Louisiana.

"There's a huge mix around the world of what various states, cities, countries, provinces, and regions are doing," Root said. "Massachusetts, Colorado, and California, for example, require that recycled water used in cooling towers or aerosolizing fixtures must be free from Legionella."

Internationally, the variety of legislation is even greater. France focuses its regulations on cooling towers and healthcare hot water systems. Meanwhile, Germany, the United Kingdom, and Italy apply broader rules covering dozens of Legionella species. Canada, on the other hand, has national directives centered specifically on Legionella pneumophila, the pathogen most closely linked to disease.

Legionella Regulation Promotes Successful Outcomes

Root highlighted the difference in outcomes between jurisdictions that regulate all Legionella species versus those that focus more narrowly on Legionella pneumophila, the agent that causes Legionnaires' disease.

"Based on data, countries that are focusing on Legionella pneumophila are actually more successful when the success measure is case numbers," she said.

To illustrate this, Root points to Quebec and New York City. Both cities enacted cooling tower laws after major outbreaks in 2012 and 2015, respectively. Following the 2012 outbreak, Quebec now requires testing specifically for Legionella pneumophila. Meanwhile, since the 2015 outbreak, New York has tested for all species. Adjusted for population, Quebec achieved a 130% better reduction in cases of Legionellosis compared to New York.

France offers another example. By directing resources toward Legionella pneumophila, the country has seen 50% less case growth compared to Germany, the U.K., Spain, and Italy, where rules for the bacteria are species-wide.

Root said that focusing regulation on Legionella pneumophila rather than casting a wide net helps areas across the globe see fewer outbreaks.

"The data make me think that their success is due to focusing their actions and remediations on the actual pathogen and not the surrogate or indicator species," Root said.

Proactive Rules vs. Reactive Outbreak Interventions

Root said lawmakers write too many regulations in reaction to a crisis instead of anticipating one. This reactive approach forces lawmakers to focus on a single fixture type—like cooling towers, potable water lines, or spas—rather than universal, building-wide risks they can regulate broadly.

"What we should be doing is paying attention to what's already been done, how effective it's been, and where the gaps are," Root said. "Take the best of those things and put them to paper. Write rules and regulations in a sort of outlined form that we all agree on."

Root recommends using ASHRAE 188 from the American National Standards Institute (ANSI), with a specific focus on Guideline 12 as a framework for proactive water management. These standards help building owners and water treatment providers assess risks systematically and apply simple but powerful practices.

Root summarized the strategy in simple terms.

"Keep the hot water hot, keep the cold water cold, keep the water moving, and keep a decent disinfectant," she said.

Professional Guidance for Points to Specificity

For legislators, Root emphasizes that water management planning is not as complicated—or costly—as it might seem.

"Testing is not difficult. Control measures are not difficult," Root said. "Once lawmakers understand that, they can become champions."

Root points to testimony she has given on Legionnaires' disease in New Jersey and elsewhere, where openness to scientific evidence quickly turned into bipartisan support.

"The CDC says that more than 90% of the time, we can prevent this disease from happening," Root said. "When lawmakers hear that, they become very empowered."

Root also has advice for water utilities and labs that interact directly with lawmakers and building owners.

"Use ASHRAE 188 to the best of your ability when you're helping a customer implement a water management program," she said. "Be diligent about your risk analysis. Start with the simple things first."

She also recommends testing specifically for Legionella pneumophila.

"When you find pneumophila, you know you have a problem. When you find species, it's unclear," Root explained. "Testing for pneumophila protects public health while also saving building owners money."

Recent modeling from Italy supports this cost-effective testing approach, showing that monitoring Legionella pneumophila reduces expenses by 27% compared to testing all species, without compromising safety.

Building Smarter Legionella Global Standards

Root sees progress in the increasing collaboration between countries and organizations. She encourages professionals to stay engaged, share data, and advocate for standards that are both scientifically sound and practical.

Although Legionella prevention is a global challenge, it's one with proven solutions. As outbreaks increase, legislation must move beyond reaction toward consistent, proactive standards that address the pathogen causing illness—Legionella pneumophila. With the right approach, water professionals can help turn patchwork rules into a coherent strategy that saves lives.