Mayor Mamdani Announces Sweeping New Measures to Strengthen New York City’s Response to Legionnaires’ Disease

Mayor Mamdani Announces Sweeping New Measures to Strengthen New York City's Response to Legionnaires' Disease

September 1, 2026 - Today, Mayor Zohran Kwame Mamdani and the New York City Health Department announced a series of new measures to strengthen the City's education, enforcement and response to Legionella bacteria in cooling towers following the Upper East Side community cluster earlier this summer.

The initiatives build on the Health Department's rapid and aggressive response to the Upper East Side cluster, including unprecedented steps to increase transparency and accelerate the remediation of cooling towers in the affected area.

"New York City responded to this summer's cluster of Legionnaires' disease with urgency and an unprecedented level of action. When New Yorkers' health is at stake, government cannot wait for the crisis to pass before asking how it can do better. Our response to the Upper East Side cluster was fast and aggressive, and we are building on what we learned to make our systems stronger, enforcement faster and public health response more transparent," said Mayor Mamdani. "New Yorkers deserve a government that moves with urgency to keep them safe."

"Our first responsibility is to protect the health and safety of New Yorkers," said Deputy Mayor for Health and Human Services Dr. Helen Arteaga. "These measures build on the Mamdani administration's unprecedented response to this summer's cluster and strengthen the systems that protect New Yorkers from Legionella bacteria year-round. This is what public health looks like when government is coordinated, measured, and responsive."

"New York City already has some of the most rigorous cooling tower laws and regulations in the country, but rigorous standards only matter if we are constantly working to make them stronger," said NYC Health Commissioner Dr. Alister F. Martin. "Today's announcement reflects our commitment to continuous improvement and investment we need to respond faster and more effectively when New Yorkers' health is at risk."

"Education, outreach, and efficient government processes are critical to delivering the services New Yorkers deserve, and we remain committed to providing our sister agencies with the information and support they need," said Department of Buildings Commissioner Ahmed Tigani. "We are proud to continue working closely with our partners in Health as we look for ways to strengthen our efforts and better serve and protect New Yorkers."

The new measures include:

• Identifying potentially unregistered cooling towers by developing synergy between the Health Department and the Department of Buildings (DOB) in the City's registration and tracking systems.
• Enhancing public visibility and transparency regarding cooling tower regulations by adding a mapping feature to the Health Department's address-based cooling tower lookup tool.
• Exploring faster culture testing methods and novel testing approaches to decrease the amount of time it takes to test and confirm positive results.
• Accelerating enforcement of cooling tower violations by assigning the earliest Office of Administrative Trials and Hearings (OATH) date that rules permit.
• Convening a scientific advisory panel to evaluate emerging cooling tower technology and alternative cooling systems.

Strengthening Education and Awareness

To increase public education and transparency before a Legionnaires' disease investigation is underway, the Health Department will expand its existing online, address-based cooling tower lookup tool with a citywide mapping feature that will allow New Yorkers to see registered cooling towers across the five boroughs.

Users will be able to review each registered cooling tower's inspection history, including compliance with Legionella sampling requirements.

To ensure New Yorkers are aware of the new tool, the Health Department will launch an annual public education and media campaign ahead of cooling tower season each summer. The mapping tool and campaign are expected to launch by spring 2027.

Improving Enforcement and Prevention

Strong enforcement of the City's cooling tower laws and regulations is critical to protecting public health and promoting compliance with requirements designed to reduce the risk of Legionnaires' disease.

When a building owner receives a summons for violating cooling tower regulations, the owner may appear before OATH to contest the violation. Unless a fine is paid in advance, collection may not occur until after the hearing. Since May 8, the Health Department has conducted 800 field inspections, over 460 of which resulted in at least one violation, and $80,500 in fines have been paid.

Under new procedures, the Health Department will assign the earliest hearing date permitted - 15 days after service of a summons. The City implemented this approach during the summer, helping accelerate the hearing process and strengthen enforcement.

The Health Department will also intensify efforts to identify and prevent the operation of unregistered cooling towers.

No cooling tower should be operating in New York City without being registered. Yet the Health Department identified unregistered cooling towers during both the Upper East Side investigation and last year's Central Harlem cluster investigation.

Going forward, the Health Department will work with the New York City Department of Buildings to strengthen connections between the Health Department's Cooling Tower Registration Portal and DOB's construction permitting system. The agencies will also work together to educate developers about cooling tower requirements before systems begin operating. This change will formalize an existing partnership that has helped identify unregistered cooling tower and will ensure more cooling towers are registered before they are ever turned on. By connecting the two systems, this will help ensure more cooling towers are registered in the first place before they are ever turned on. The new measures are expected to be implemented by the end of the year.

Convening a Scientific Advisory Panel

Rising temperatures, longer heat waves, and high humidity for longer periods of the year are creating conditions that can increase the risk of Legionella bacteria growth in cooling towers.

Cooling towers already provide conditions favorable to Legionella growth. As climate change drives more extreme and prolonged heat, it is increasingly important to invest in proactive measures that reduce the public health risks associated with these systems.

In response, the Health Department will convene a scientific advisory panel to evaluate emerging cooling tower technology and explore alternative cooling technologies that could reduce New York City's reliance on cooling towers.

The Health Department will appoint the panel's chair and members in the coming months and aims to issue recommendations within the next year.

Strengthening Investigation and Response Times

One of the defining challenges of the Upper East Side investigation was the density of cooling towers in the affected area - nearly four times as many as were identified during the Central Harlem cluster in 2025. Each tower needed to be sampled and tested for Legionella as quickly as possible.

In the coming years, the Health Department will explore faster culture methods and novel testing approaches, including to reduce the time it takes to test and confirm positive results. This will allow the Public Health Lab to rapidly scale up testing during a Legionnaires' disease cluster while providing additional capacity for other emerging issues. This requires additional staff and resources, which the Health Department aims to have in place before the summer of 2028.

Upper East Side Community Cluster

The Health Department continues to investigate potential sources of exposure associated with the Upper East Side community cluster. Results from whole-genome sequencing analysis are expected this fall.

That analysis compares the specific strain of Legionella found in patient samples with strains identified in cooling towers in the affected area. If genetic matches are identified, the analysis may provide additional information about the source of this summer's cluster.

As of August 31, there have been 94 cases of Legionnaires' disease associated with the cluster. No patients remain hospitalized, and 11 people have died.

As of late August, 81% of cooling towers citywide were in compliance with monthly requirements to sample and test.

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