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NYC Legionella inspections rose only gradually before latest Legionnaires' cluster in Manhattan

By

Joe Hong

Published Jul 6, 2026

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Legionella testing

MD Zakir Mahmud/Getty Images

By

Joe Hong

Published Jul 6, 2026

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City inspections of cooling towers — meant to prevent the spread of deadly Legionella bacteria — rose only gradually since last year’s near record lows, according to a Gothamist analysis of public data and numbers provided by New York City's Department of Health and Mental Hygiene. In over 20% of buildings, owners had not submitted required test results in the first five months of 2026.

The sluggish rate of compliance came ahead of a new cluster of Legionnaires’ disease the health department identified on the Upper East Side late last week. It also follows a deadly outbreak in Central Harlem last summer that killed seven people, hospitalized 90 and sent the Adams administration scrambling to get it under control.

Health officials are now investigating a cluster of at least 14 cases of Legionnaires’ disease cases in the Carnegie Hill and Yorkville neighborhoods in Manhattan, all located in the 10028, 10075 and 10128 ZIP codes. The health department said it is inspecting all cooling towers in the affected blocks, and the agency released a video of health commissioner Alister Martin going door to door on the Upper East Side informing residents that the disease is likely spreading in the area.

The latest cluster was identified as the city was in the grips of an unprecedented heat wave, with heat index values reaching 110 to 115 degrees — weather that allows Legionella bacteria to thrive. The rush to contain it is reminiscent of last July, when health officials under then Mayor Eric Adams first identified the outbreak in Central Harlem.

In the months leading up to that public health emergency, the city had inspected 59% fewer cooling towers than it had when Adams first came into office in 2022. Health officials at the time attributed the decline to short staffing and budget cuts.

Gothamist’s analysis by the numbers:

Now, as of late June of this year city employees have only inspected 1,306 of the nearly 6,000 cooling towers in the city since the start of 2026. It’s only a slight increase from 2025, when the city inspected 1,156 cooling towers over the same period before the outbreak began last July.

Those numbers pale in comparison to the more than 3,000 inspections in the first six months of 2017, when the city first implemented cooling tower regulations. Chantal Gomez, a spokesperson for the health department, said the agency “forecasts” that it completed 114 more inspections in June that had yet to be included in the data provided to Gothamist, which would bring the total to 1,420 for this year, 23% more than last year.

In the ZIP codes included in the latest cluster, 48% of the 179 cooling towers went over a year without an inspection by the city, five points lower than the rate across the five boroughs. About 26% of the towers in the outbreak area have no record that building owners tested for Legionella bacteria in 2026. That’s roughly four points higher than the citywide rate.

Mayor Zohran Mamdani’s office did not respond to questions about the small increase in the number of inspections since his predecessor left office and what it was doing to prevent additional outbreaks.

Local law authorizes the health department to conduct unannounced inspections of cooling towers. Gomez said the agency aims to inspect every cooling tower once a year.

But by that measure, the city is also falling far behind. As of April 17 of this year, more than half of the city’s cooling towers had not been inspected in over a year, according to Gothamist’s analysis of the most recently available data.

After Gothamist reported on the staffing shortfall, the city’s health department sought to increase its ranks of “water ecologists” who inspect cooling towers, which operate as part of a building’s air conditioning system and can spread the bacteria that causes Legionnaire’s disease over an area of several city blocks.

Gomez, the health department spokesperson, said the agency now has double the number of inspectors compared to last year. She said the new hires were in training for “several months” and did not conduct any inspections in May or June.

Gomez said having additional staff will allow the department to increase inspections and that she expects the number of routine cooling tower inspections to increase as new staff continue to be onboarded.

New testing requirements

The health department implemented new requirements in May for building owners to test their cooling towers for legionella bacteria every 31 days, up from the previous requirement of every three months. The new requirements were created by city lawmakers in response to last summer’s outbreak. Gomez said implementing that change reduced the agency’s ability to conduct more cooling tower inspections, but did not provide further explanation.

It’s unclear how well building owners are complying with the enhanced testing requirements. According to a Gothamist analysis of city data, out of the 5,944 active and registered cooling towers in the city, one in five had not submitted a test for legionella bacteria this year as of May 21, the most recent date that data was publicly available.

The 31-day testing mandate went into effect on May 8, and is required for cooling towers that have been turned on during warmer months when Legionella bacteria is most likely to spread.

Gomez said missing tests could mean that the tower is currently not running or started running more recently.

April McIver, executive director at The Plumbing Foundation City of New York, an advocacy group for building water systems professionals, said city inspections are critical for keeping building owners accountable.

“We’re always going to be supportive of more inspections that can prevent death,” she said, adding that regulations rely on both health department enforcement as well as diligence from building owners.

Cooling towers circulate cold water throughout larger buildings to absorb heat. The warmed water is then pumped into a cooling tower on top of a building where it is blown out by fans as vapor.

Without proper treatment and monitoring, warm, stagnant water can foster the growth of legionella bacteria, which can cause a type of pneumonia if the water vapor is inhaled by passersby.

City regulations acknowledge the important roles of both the Department of Health and building owners in preventing the spread of Legionnaires’ disease. Fines for building owners failing to conduct testing for Legionella can range between $2,000 and $4,000.

City health inspectors found that last year’s outbreak was caused by two cooling towers on two city owned properties. The first was located at Harlem Hospital. The second was at a nearby construction site managed by the construction company Skanska for a city public health lab.

A Gothamist investigation found that the hospital had failed to abide by its own maintenance plan and conduct regular testing for Legionella. An investigation completed by the health department found that the cooling tower at the construction site had not been registered or tested.

Health officials urge anyone who lives in the area or has visited since late June to contact a health care provider if they develop flu-like symptoms. New Yorkers who need help finding a provider can call 311 or (844) 692-4692.

Tagged

Health and Science

Zohran Mamdani

new york city

Joe Hong

Joe Hong is the investigative data reporter for WNYC and Gothamist. He previously covered K-12 education for several newsrooms across California. His reporting has led to local reforms in juvenile justice system as well as a state law requiring universal screening for dyslexia. Got a tip? Email [email protected]

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