JULY 14 — NEW YORK ON THE LEGIONNAIRES’ DISEASE OUTBREAK — ON IT!

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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.

NYC is in the middle of a large Legionella outbreak, and the city is racing to contain it. Notably, this response feels different. For the first time, buildings that test PCR positive are being named publicly, more than 100 health department employees are working nonstop on the response, and communications have been far clearer than during previous outbreaks. This week, emergency physician and friend of YLE Jeremy Faust wrote a great piece highlighting the many ways New York is getting the response right. I’m excited to share his perspective in this guest post. And I’ll be back with some of my own thoughts later this week.


Lindsey Nicholson/UCG/Universal Images Group via Getty Images.

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.

  1. 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.
  2. 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.
  3. 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.
  4. 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. 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.

  1. 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:

CDC information:

  1. Transparency check: New York City’s Health Commissioner, Dr. Alister Martin, is a friend and former mentee of mine (Jeremy’s). 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.

Thanks for your financial support of Your Local Epidemiologist in New York! I couldn’t do this without you. — Marisa

Share Your Local Epidemiologist — New York

 

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JULY 14 — OVERWHELMING SUPPORT FOR REPORTING SCIENCE RESEARCHING, REPORTING AND ALERTING DEVELOPMENTS TO THE PUBLIC. WITHOUT PRIOR HEALTH DEPT. APPROVAL…

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The YLE team is back from summer break, tanned (some of us), rested (debatable with small kids), and ready to jump right back in.

I know a lot of you have questions about the Cyclospora outbreak. The YLE team is collecting them all, and tomorrow I’ll pick the top 10 for a deep dive. As of this morning, there is still very, very little communication from HHS, which is pretty insane.

In the meantime, here’s what’s going on with health this week, including other bugs like ticks and mosquitoes. Expect trucks to be spraying insecticide soon, and let’s celebrate an enormous public response to a new proposed federal rule.


Disease weather report

Cyclospora keeps climbing

Cyclospora cases continue to climb. Some of this is expected, since more people are now aware of it and testing for it, but it is still an undercount, given that many people wait out the sickness at home.

The total number of cases is hard to pin down. This is because data in the U.S. is decentralized (local health departments report to states, states report to the CDC), so you will likely see numbers all over the place. If we scrape for state-level data, the most cases (2,640) are in Michigan, followed by New York (470). A local health department in Northwest Ohio is reporting 661 cases.

Figure from the Health Security Operations Center

While there are cases in over 30 states, the U.S. sees cases every year, often from different outbreaks. A key question is whether the number exceeds expectations and, if so, why. In some states, this is certainly the case. For example, the number of infections in Michigan is 31 times higher than in previous years, and in New York, it’s three times higher. In some states, like California, rates are not higher than normal.

Michigan’s health official announced yesterday that preliminary findings indicate lettuce or packaged salad greens as a likely source. The investigation has yet to pinpoint a company or rule out other foods. Two dozen other states are still under active investigation. Zero word from FDA.

What this means for you: Continue to avoid bagged and boxed salads at grocery stores and restaurants. I’m still sticking to produce that can be peeled or vegetables with smooth surfaces, like cucumbers, until more data comes in.

Ticks are backing off

We’re well on our way down for tick season. Activity tends to drop off as we move deeper into the heat of summer.

Source: CDC; Annotated by Hannah Totte at Your Local Epidemiologist

Why? Ticks are prone to drying out, so in peak summer heat they retreat into moist, shaded leaf litter rather than questing (climbing grass to grab a host), which reduces host-seeking activity even if the tick population hasn’t shrunk. This dip also lines up with the tick life cycle: nymphs, responsible for most Lyme transmission, peak in late spring/early summer, then quiet down in the hottest weather before adults pick back up in fall.

Mosquitoes taking over

As ticks recede, mosquitoes take over and with them, the rare diseases they can carry. The most common one in the U.S. is West Nile.

Peak mosquito season is still about a month out, but the CDC is already flagging an unusually early surge in West Nile virus (WNV) activity this year. They have flagged 48 cases across 23 states detecting the virus, which is more than five times the historical average for this point in the season.

Source: CDC. Annotated by Hannah Totte at Your Local Epidemiologist

What this means for you: Most people infected with WNV never even know it because ~80% have no symptoms. But older adults and those who are immunocompromised can develop serious neurological illness. Start being consistent with using an EPA-registered repellent (with DEET or picaridin), dumping standing water around your home, and using screens at dusk and dawn. You may also start seeing mosquito spraying trucks. (See more below.)

Heat blanketing the North

This week, a large swath of the northern U.S. is facing the most extreme heat risk category. If you’re in the purple or red areas, everyone is at risk and needs to take action. Heat kills more people in the U.S. than any other weather event.

Source: NOAA; Annotated by Hannah Totte at Your Local Epidemiologist

What this means for you: Check on elderly neighbors and relatives, hydrate before you’re thirsty, and move strenuous outdoor activity to early morning or evening if you can. Here are 6 things to know about heat-related illness from the YLE team.

World Cup Health Security Center Update

We’re nearing the end of the World Cup tournament (the final is on July 19!), and there have been no major outbreaks tied to the games, aside from heat-related illness. A few teams reported minor illnesses among players.

Measles remains the primary focus of monitoring. There are a number of cases passing through major airports (far more than in any other year), particularly near the World Cup games. While it will be very hard to track, we could very well see outbreaks across the world following the World Cup.


Spotlight: Why is that truck spraying my street?

With mosquito activity picking up and the U.S. having a particularly bad start to the season, you may start noticing spraying trucks in your neighborhood. Where they go is driven entirely by your local public health or vector control department’s surveillance data. Departments set traps to collect mosquitoes, send batches to a lab, and test them.

When lab tests consistently yield positive results, insecticide is then sprayed in the affected area. The spraying itself does two things:

  1. Kill flying adult mosquitoes by spraying very small amounts of adulticides into the air. This spray is a fine mist that acts as a fogger.
  2. Kill larvae by applying larvicides directly to the water where mosquito larvae have been detected. This helps kill more hard-to-reach areas.

People rightfully have many questions about whether these insecticides are safe for humans. They are safe because the dose and where they are applied are very purposeful. These insecticides work by overstimulating insect nerve cells until they’re paralyzed, but insect nerves are far more sensitive to the chemical than ours, and mosquitoes are tiny, cold-blooded, and can’t break the chemical down the way we can. So the same dose that’s fatal to them is far too small to hurt a person. How these insecticides are used also matters. Adulticide sprays are released as low-volume mist, and the droplets disperse and degrade quickly, resulting in very low human exposure. Larvicides are placed directly in standing water and target larvae through mosquito-specific biological mechanisms.

A 2025 review of community mosquito-control spraying found no causal relationship between adult mosquito-control applications and adverse human health impacts when applied appropriately, with estimated exposure levels far below regulatory concern.

People with asthma and other respiratory conditions are particularly concerned. But an older study in New York City found no increase in asthma visits, including among children, after West Nile spraying.

What this means for you: Reducing WNV is important, and spraying is safe. I’ll stay indoors during spraying when I can but won’t lose sleep over it. Check with your local public health or mosquito control department for the schedule—they’re supposed to publish one.


Good news

  • More than 341,000 comments were submitted on the OMB’s proposed rule that could, quite literally, break science in the U.S. This is an enormous public response by any standard; public comment on federal rules almost never gets anywhere close to that volume. Way to show up for science discovery in the U.S.! Comments are now closed, and it’s time to see how the federal government responds.

Bottom line

From salad choices to mosquito bites to heat safety, this world just never gets boring. Stay healthy out there.

Love, YLE


Your Local Epidemiologist (YLE) comprises a team of experts, ranging from physicians to immunologists to epidemiologists to nutritionists, working together with one goal: to “translate” ever-evolving public health science so that people are well-equipped to make evidence-based decisions. The YLE suite of newsletters reaches over 475,000 people across more than 132 countries. This newsletter is free to everyone, thanks to the generous support of fellow YLE community members. To support the effort, subscribe or upgrade below:

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JULY 14 –SENATOR GILLEBRAND BACKS GOV. HOCHUL MORATORIUM ON HIGH IMPACT DATA CENTER FACILITIES

GILLIBRAND STATEMENT ON NEW YORK STATE DATA CENTER MORATORIUM

New York, NY – Today, U.S. Senator Kirsten Gillibrand released the following statement regarding Governor Kathy Hochul’s executive order to implement a one-year pause for hyperscale data centers to assess for environmental impact:

“I applaud Governor Hochul for taking decisive action on data center construction. Today’s executive order sends a clear message New Yorkers deserve a say in how this technology impacts their lives and communities.

“This one-year moratorium is fundamentally about trust. Right now, New Yorkers aren’t convinced these massive facilities benefit them. Before we move forward, our communities need ironclad guarantees that their energy bills won’t spike, their water will be protected, and their air will remain clean.

“At the federal level, my mission is to ensure AI innovation benefits every American, not just a powerful few. That requires establishing clear, reliable rules of the road. We must build a framework that protects our kids from harmful algorithms and social media tools; shields seniors and consumers from AI-driven scams and fraud; and safeguards American jobs and livelihoods from displacement.”

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