How New York is winning against Legionnaires' Disease
Fast testing, aggressive remediation, and transparent communication are keeping a potentially larger outbreak under control—and offering a model for public health done right.
Even its name should summon effective public health: Legionnaires’ Disease. The designation was initially suggested by the media during an intense investigation into a frightful pneumonia cluster at a 1976 gathering of The American Legion. Eventually, though, after successfully pinning down the cause, CDC scientists embraced the moniker too.
In the famed inquiry, now considered a classic case study still taught in schools, CDC sleuths determined that the responsible pathogen was not primarily spreading from person-to-person. Instead, a common source was found—the convention hotel’s air conditioning system. Bacteria had grown in the cooling towers. Emanating mists eventually circulated throughout the hotel. Soon, over 180 became ill, and 34 died.
So, both the common and official scientific name, Legionella pneumophila, convey the end result of a process, the hard, essential work of public health. The very one that has been under attack during the second Trump administration.
Recall what then-presidential hopeful Robert F. Kennedy Jr. said in 2023, prior to becoming our nation’s top health official in 2025: “We’re going to give infectious disease a break for about eight years.”
That was profoundly stupid then. It’s even worse now.
Juxtapose that against a contrasting idea: “When public health works, there are no headlines.”—Unknown.
There, friends, are your extremes. In the first case, there is sympathy for the ostrich, head buried, tail up. In the second, inglorious (even mundane) behind-the-scenes preparation anticipates future threats by acknowledging that crystal balls don’t exist. The only way to prepare for one rare event is to prepare for many.
The only way to stop outbreaks are to discover them.
Clearly, New York City officials subscribe to the second approach. Actually, when it comes to modern approaches to Legionnaires’ Disease, they didn’t just read the book—they wrote important new chapters in it. Accordingly, they’ve done everything possible to keep a recent outbreak of Legionnaires’ Disease relatively beige.
While not as newsy as incompetence would be, it’s worth celebrating good technique. In fact, that’s what Inside Medicine is for. So, let’s talk about why public health is winning New York City’s current battle with Legionnaires’ Disease.1
What’s going well.
Let’s check in on five domains in New York’s response. Data, resources, technique, innovation, and communication.
Data. The city is providing updates on case counts. Easy-to-find, easy-to-understand information reassures the public that their leaders are engaged, and that they trust their constituents. As of Sunday, there were 59 total cases (15 currently hospitalized, 33 discharged, 11 not hospitalized, and 0 deaths). Consider the opposite posture—Trump’s infamous line in the early days of Covid, “If we didn’t do any testing, we would have very few cases.” The ostrich approach insults the public’s intelligence, and increases risk. New York City has chosen the better path.
Resources. Once an outbreak has been detected—if you detect it at all—the ground game begins. In a Legionnaires’ outbreak, finding the source is everything. To do that, you have to test the water from the cooling tower systems in the area where cases are popping. To do that, you have to have people. (This is why you don’t mindlessly RIF public health employees, Elon.) Here, the city deployed its teams, over 100 staff, to the Upper East Side of Manhattan, to test tower-by-tower for Legionella. That’s how you do this.
Technique. New York City officials’ technical prowess centers on not waiting around. Rather than waiting for case counts to mount before deploying teams, city policy mandates an investigation whenever two or more potentially linked cases have been identified. In this case, water cooling towers are being tested, even if there have not yet been cases among residents served by them. On Friday, officials announced that water cooling towers serving 31 buildings had been identified. Rather than stoking panic, this information directed action. By Sunday, all of the relevant infrastructure had already been cleaned, meaning it was safe. And because every water cooling tower in the area was tested quickly, the response could be right-sized. There was no need to treat the many units that tested negative (and have not been associated with suspected cases). New York City officials spurned the ostrich.
Innovation. In prior outbreaks, health officials tested water cooling towers rapidly but waited until bacterial cultures were positive before requiring full cleaning and disinfecting. Here’s what the Mayor’s office wrote in an email about the new policy:
“For the first time ever, the NYC Health Department is requiring all buildings with a PCR positive screening test to clean and disinfect their cooling towers. Previously we required buildings with registered cooling towers to do an initial boost of the chemical that kills the bacteria when the PCR test was positive, which is already an effective measure for protecting human health. The full cleaning and disinfection reduce the risk that any living Legionella bacteria that was present in the cooling tower will grow back. This more aggressive strategy is designed to facilitate a rapid remediation response and reduce the potential for ongoing exposure. The first batch of towers has already completed the treatment process and others are in process.” —New York City Office of the Mayor (email).
It’s important to note that more isn’t always better. There’s such a thing as overdoing it. But this escalation makes sense. The likelihood of a false positive on an initial PCR test is currently low, given the known outbreak. Waiting for the confirmatory step (bacteria growing out in culture) would therefore represent an unnecessary delay. So, in this case, doing more sooner makes sense.
Communication. The city's health department is way out in front of this. There’s no need for a university or media publication to throw up a dashboard because the city is providing official counts, with frequent updates. They’ve clearly messaged that there may be more cases, owing to incubation times, and this is to be expected. They’ve given their residents the information they need without fear-mongering. They’ve published press releases, updated their health information both for the public and for public health professionals/medical providers, and held public town halls. They’ve also cooperated with local and national media. Heck, they even answered my annoying questions all weekend.
Leading by example. “No notes.”
How often do we find ourselves bemoaning something broken in public health? Too often. So, it’s refreshing to see public health crushing it. Yes, I’m biased, because New York City’s health commissioner Dr. Alister Martin is a friend and former mentee. That also means that if he and his team were fumbling, I’d be working the phones trying to advocate for course corrections. In this case, I’ve got virtually nothing to offer them by way of advice, so far.
But don’t take my word for it. I asked Dr. Demetre Daskalakis, former Director of the CDC’s National Center for Influenza and Respiratory Diseases (who previously served in New York City’s health department from 2014-2020) what he thought of the current response. He agreed that the department has performed admirably here.
“No notes,” he added.
In a time when federal programs have been hampered by cuts, making it far harder to respond to new problems (#ExplosiveDiarrhea), New York City’s prompt actions in the current Legionnaires’ outbreak are a welcome reminder that public health, done by genuine experts, actually works.
Resources:
Some of New York City’s resources, including two peer-reviewed publications on their approach to Legionnaires’ Disease:
Legionnaires’ Disease and Building Evaluations. (An interesting technical readout, for anyone interested.)
Outbreak of Legionnaires’ Disease Associated with Cooling Tower Systems in Central Harlem. (This came out in late June, describing a 2025 outbreak. Nice timing.)
Spatio-Temporal Cluster Detection for Legionellosis using Multiple Patient Addresses.
CDC information:
Thank you for reading! If you have information about any of the unfolding stories we are following, please email me or find me on Signal at InsideMedicine.88.
Transparency check: New York City’s Health Commissioner, Dr. Alister Martin, is a friend and former mentee of mine. I’ve agreed to participate in a “NYC Health Preparedness and Communications Roundtable,” but I have not yet done so, nor have I advised anyone in the department on this issue.
It is heartening to see public health done right. Thank you for informing us, as usual! Those of us who have lost friends, family, or colleagues to Legionnaire’s know how vital preventing /controlling outbreaks is.
These are proactive steps, and they should serve as a model for outbreak response — especially against jurisdictions that won't even disclose which cooling tower caused an outbreak. (In Marshalltown, Iowa, the state suggested naming the tower would be like disclosing someone's private health information. Apparently cooling towers are people too in Iowa.)
But the harder question for New York's mayor and his new health commissioner is whether they'll confront the flawed policy decisions the Adams administration made during the last major Legionnaires' outbreak tied to Harlem Hospital — the facility's second in just a few years.
Two things. First, transparency: for nearly a decade the City ran an open cooling tower registration and compliance portal the public could search. The Adams administration shut down that access during the outbreak — but not before reporters were able to document repeated regulatory failures at public buildings.
Second, and more important: NYC Health walked away from the letter and intent of its own regulations. I know, because I wrote them, in lockstep with the global consensus (drawing heavily on the UK's Health and Safety Executive): site-specific risk assessment, written water management plan, a program to implement it, and validation with corrective action. The City's job was to check two things — did the owner do the minimum the rules require, and did the owner follow its own plan? During the H+H outbreak, NYC Health reversed the long-held position of the program's two founding assistant commissioners and claimed owners weren't expected to follow their plans, so it wouldn't enforce compliance. Reporters documented serious failures by H+H even as the City insisted there were no Health Code violations. Compliance problems disappear once the regulator declares the rule unenforceable. https://gothamist.com/news/harlem-hospital-failed-to-follow-its-own-guidelines-before-legionnaires-outbreak
The City should use this latest outbreak to look honestly at how the regulations are actually implemented. There is no independent oversight at the building level — the same private parties the owner retains both implement the plan and validate it. And now that NYC Health says it doesn't assess whether a tower is maintained according to the plan, that last external check is gone too. Owners write their own plans, grade their own work, and answer to no one who's looking. That is essentially no oversight at all.
Much of the fix is administrative: reopen the portal, restore plan compliance as a basis for enforcement. But the real reform is structural. New York already bars an elevator inspector from being affiliated with the company that maintains the elevator — a rule the Department of Buildings adopted specifically to prevent this kind of conflict of interest. High-pressure boilers can't be self-inspected either; an outside DOB-authorized inspector must examine them and file with the Department, which audits and can inspect on its own. A cooling tower that can seed fatal pneumonia across a neighborhood belongs in that same category. Fully independent oversight would end the fox-guarding-the-henhouse setup and give the City verification it doesn't currently have. A response this good in an emergency should be matched by a system built to prevent the next one.