Mayor Mamdani Takes Aggressive Action to Address Upper East Side Legionnaires’ Disease Community Cluster

NEW YORK - Mayor Zohran Kwame Mamdani and the New York City Health Department today announced additional emergency measures to respond to the Legionnaires' Disease community cluster on the Upper East Side that has sickened at least 23 people as of July 6.

After identifying just two cases that suggested a possible community source on Thursday, July 2, Mayor Mamdani directed the Department of Health to immediately begin testing cooling towers across the affected area and launch community outreach ahead of the holiday weekend. The Department mobilized more than 100 staff members to carry out the investigation.

As part of this response, the Administration will take an unprecedented step of publicly releasing the addresses of all buildings whose cooling towers test positive for Legionella bacteria during the initial PCR screening process. Buildings with positive initial tests are also being ordered to immediately drain, clean and disinfect their cooling towers to reduce the risk of further exposure.

"When there's a public health threat, New Yorkers deserve urgency and transparency from their government," said Mayor Mamdani. "That's why we're using every tool available to protect people by moving quickly to identify potential sources of exposure, requiring immediate remediation and making sure New Yorkers have the information they need to keep themselves and their families safe. If you live, work or recently visited the area and are experiencing symptoms like fever, cough or difficulty breathing, please contact a healthcare provider as soon as possible."

"Our administration is increasing the speed with which it responds to the spread of Legionnaires' Disease and improving systems that keep the public informed," said Deputy Mayor for Health and Human Services Dr. Helen Arteaga. "New York City is aggressively identifying, cleaning and disinfecting cooling towers that test positive for the presence of Legionella bacteria, and while our administration works to address this public health emergency, we urge everyone in the area, especially older adults and other vulnerable communities, to seek care if they develop flu-like symptoms."

"More than 100 NYC Health Department staff members have worked nonstop since the start of this cluster as we take aggressive action to ensure that we are cutting off the source of exposure as quickly as possible," said NYC Health Commissioner Dr. Alister F. Martin. "The Mamdani administration is taking unprecedented steps, not just to cut off the source of exposure, but to keep New Yorkers informed on what's happening. We urge New Yorker who live or work on the Upper East Side to seek medical care if they are experiencing flu like symptoms. We look forward to providing more information in the coming days."

The City's immediate priority is stopping any further exposure by rapidly identifying and remediating cooling towers that may contain Legionella bacteria. Cooling towers release mist into the outside air and have been identified as the source of previous community outbreaks of Legionnaires' disease.

Under this response, any building whose cooling tower tests positive during the initial PCR screening test will receive a Commissioner's Order requiring immediate remediation, including draining, cleaning and disinfecting the towers immediately.

In previous community clusters investigations, buildings with positive PCR results were initially required to boost chemical disinfectant levels while awaiting confirmatory culture testing, a process that can take up to two weeks. Full cleaning and disinfection was generally required only after a positive culture result.

This year, the City is taking a more aggressive approach by requiring full remediation immediately after a positive PCR result, accelerating the response and reducing the possibility of ongoing exposure. Several building owners have already completed remediation, while others are actively carrying out the required work.

The Upper East Side has a high concentration of cooling towers - more than three times the number tested during the 2025 Central Harlem investigation. As of July 6, 2026, approximately 160 cooling towers are registered within the three ZIP codes under investigation, though not all are operating or located within the investigation zone.

As of July 6, 2026, Health Department staff had collected samples from 139 cooling towers. The remaining operating towers will be sampled, if operating, within the next 24 hours.

The Health Department will release the addresses of all buildings whose cooling towers test positive on the PCR screening test as results become available.

The Health Department launched its investigation July 2 after identifying two Legionnaires' disease cases in close proximity in Carnegie Hill and Yorkville (ZIP codes 10028 and 10128). Although a community cluster is typically defined as three or more cases linked by location and time, the Health Department initiated its response immediately rather than waiting for additional cases.

On July 5, ZIP code 10075 was added to the investigation after another confirmed case involving someone who lives, works, or recently visited that area.

As of July 6, 23 people have been diagnosed with Legionnaires' disease connected to this cluster. 17 people have been hospitalized, including two who have since been discharged and are now recovering at home. No deaths have been reported. The Health Department continues to test every cooling tower in the investigation area. Building owners whose cooling towers test positive for Legionella bacteria are required to complete full remediation.

Anyone who lives, works or has visited the affected area since late June and develops symptoms such as fever, cough or difficulty breathing should contact a health care provider immediately.

The Health Department issued a Health Alert to providers and has conducted community outreach since July 2, including throughout the holiday weekend. The Health Department hosted a virtual town hall on July 6 and will hold an in-person town hall tonight at 6 p.m. at St. Ignatius Loyola Wallace Hall, 980 Park Avenue. Legionnaires' disease is a form of pneumonia caused by the Legionella bacteria, which grow in warm water. People become infected by breathing in water droplets containing thebacteria; the disease does not spread from person to person.

Symptoms typically develop two to 14 days after exposure and may include fever, chills, muscle ache and coughs. Legionnaires' disease can be treated effectively with antibiotics, particularly when diagnosed early.

The Health Department reminds New Yorkers that it is safe to use air conditioners, cooling centers and other City facilities in the affected area. It is also safe to shower and drink tap water. Cooling tower mist is released outdoors and does not affect indoor air conditioning systems, window air conditioners or building plumbing. People at higher risk include adults age 50 and older, people who smoke and those with chronic lung disease or weakened immune systems.

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