In Harlem, Legionnaires Disease Spread Investigation Underway: NYC Health Department Updates

Two People on the Upper East Side Diagnosed With Legionnaires’ Disease, a Type of Pneumonia Caused by Breathing Water Vapor Containing Legionella Bacteria in the Outside Air

NEW YORK, NY — Today, the NYC Health Department has launched an investigation into a likely community cluster of Legionnaires’ disease in the Upper East Side neighborhoods of Carnegie Hill and Yorkville (ZIP codes 10028 and 10128). As of July 2, two people have been diagnosed with Legionnaires’ disease in the affected area, and confirmatory results for other potential cases are currently pending. To date, there are no deaths associated with this cluster. Any New Yorkers who currently live or work in this area or people who have visited the area since late June and are experiencing flu-like symptoms, such as fever, cough, or difficulty breathing should contact a healthcare provider immediately.

The NYC Health Department is actively investigating this Legionnaires’ disease cluster by sampling and testing water from all cooling tower systems in the area. Past community clusters have been caused by Legionella bacteria spreading through the air from the mist produced by cooling towers. Building owners with any cooling towers that test positive for the presence of Legionella bacteria will be directed to conduct full remediation.

A Health Alert is going out to healthcare providers, advising them to consider Legionnaire’s disease for people presenting with compatible symptoms, and community outreach will be conducted in the area beginning over the weekend.

Legionnaires’ disease is a type of pneumonia that is caused by the bacteria Legionella, which grows in warm water. People only get sick by breathing in water vapor containing Legionella bacteria. Symptoms resemble other types of pneumonia and can include fever, chills, muscle aches, and cough. Legionnaires’ disease is not contagious and can be treated with antibiotics when caught early.

With warm weather this [Fourth of July]  weekend, the NYC Health Department wants to remind New Yorkers that it is safe to use air conditioners, cooing centers, and all city facilities in this neighborhood. It is also safe to shower, and drink tap water. Mist from a cooling tower blows outside and does not affect the internal air conditioning, window air conditioning units, or plumbing system. Individuals at higher risk include those 50 years old and older, cigarette smokers, and people with chronic lung disease or compromised immune systems. People living or working in the area who are experiencing these symptoms should seek medical attention with a primary care provider or seek urgent care.

NEW YORK, NY —For the first time today, new citywide regulations issued by the NYC Health Department are in effect requiring building owners to test cooling towers for Legionella bacteria more frequently than anywhere else in the country.

The amendments mandate building owners test for Legionella bacteria every 31 days when the cooling tower is operating — three times more frequently than was previously required — further strengthening one of the nation’s most rigorous and protective laws. The NYC Health Department has notified building owners of actions required to meet the new cooling tower mandates and reminds them of the critical role owners play in keeping New Yorkers safe.

“The Mamdani Administration is enacting commonsense policies that prioritize New Yorkers’ health and safety,” said Deputy Mayor for Health and Human Services Dr. Helen Arteaga. “Today, we are announcing new amendments that will strengthen safety standards for cooling towers and help us respond to the existence of harmful bacteria more quickly and efficiently. As the temperatures rise, it is increasingly important that we monitor for and protect every New Yorker against Legionella, and that’s exactly what these regulations aim to do.”

“Protecting the health and safety of New Yorkers is my top priority,” said NYC Health Commissioner Dr. Alister Martin. “Today’s new regulations requiring more frequent testing of cooling towers is public health at work. We thank the NYC Mayor’s Office, City Council, and community advocates for their partnership and unwavering dedication to this issue. Together, we are building a healthier, safer future for all New Yorkers.”

“Protecting New Yorkers’ health and safety is paramount, and we are proud to work with the NYC Health Department and all of our sister agencies to help protect against Legionella,” said NYC Department of Citywide Administrative Services (DCAS) Commissioner Yume Kitasei. “As the summer approaches, we are working collaboratively to ensure that the City is utilizing every tool in the toolbox to monitor for this bacteria and help keep our residents safe.”

“The New York City Health Department continues to be the gold standard in public health oversight,” said NYC Department of Buildings (DOB) Commissioner Ahmed Tigani. “These new regulations will help owners discover a potential problem before members of their community are exposed to harmful bacteria. We are proud to continue working closely with our agency partners on ways to help protect the health and safety of our fellow New Yorkers.”

On August 29, 2025, the NYC Health Department announced the end of the Central Harlem community cluster of Legionnaires’ disease. By the end of the cluster, there had been 118 cases of Legionnaires’ disease; 92 people had been hospitalized; and sadly, seven people had died in connection with this cluster. In collaboration with the NYC Health Department, the New York City Council enacted amendments to New York City’s landmark cooling tower law, authorizing the more rigorous testing schedule to require buildings to demonstrate effective Legionella control and increase fines for property owners who fail to comply with the law. The new requirements guide building owners in improving management practices and technical capacity for even safer cooling tower operation.

The NYC Mayor’s Office proposed a package of resources and policy changes to implement these changes. The NYC Health Department was allocated an additional $13 million in the fiscal year 2027 budget to support the agency’s routine cooling tower inspections and any future response to Legionnaires’ disease clusters. This includes:

The NYC Health Department notified all cooling tower operators that the new rule is in effect and is conducting outreach and education about the requirements to help owners comply. There are approximately 4,000 buildings with registered cooling towers across the five boroughs.

The NYC Health Department is also working with other City agencies, including DCAS and DOB, to identify new ways to improve cooling tower monitoring and maintenance at City-owned buildings, including increasing awareness of a citywide contract available for maintenance, testing, and remediation services, and to strengthen the registration of cooling towers at buildings under construction.

The NYC Health Department has an extensive investigation and notification system for Legionnaires’ disease and response, investigating every case of Legionnaires’ disease and monitoring daily for patterns in cases.

Legionnaires’ disease is a type of pneumonia that is caused by a bacterium of Legionella, which grows in warm, stagnant water. People — especially those at higher risk — can get sick by breathing in water vapor if it has Legionella bacteria. Symptoms resemble other types of pneumonia and can include fever, chills, muscle aches, and cough. It is not transmitted from person to person and can be treated with antibiotics when caught early. Individuals at higher risk for Legionnaires’ disease include those ages 50 and above, cigarette smokers, and people with chronic lung disease or weakened immune systems.

If there is a pattern of multiple cases reported across a community in a short span of time, the NYC Health Department investigates cooling towers as a potential source. Cooling towers present a risk of spreading Legionnaires’ disease at a community level because they operate with warm water and their fans generate water vapor that may contain Legionella that’s traveling outside in the environment.

The NYC Health Department also evaluates a building’s internal water system when two or more cases of Legionnaires’ disease are detected at a single address in a 12-month period. Building evaluations are sporadic and the exposure is only to residents of the building. These pose no risk to the surrounding community.

“After the disturbing deaths and harm caused to individuals and families last year in the deadly Legionnaires’ outbreak, I introduced legislation to counter the danger of unchecked and contaminated cooling towers,” said State Senator Cordell Cleare.“I am encouraged that the New York City Health Department will announce the amended cooling tower regulations and enforce more frequent Legionella testing ahead of the cooling tower season. My legislation, S8472, similarly aims to strengthen New York City’s laws on cooling towers by requiring biannual certification of cooling towers and increasing fines for violations by negligent building owners. So, this amendment to the cooling tower legislation is great news.”

“New Yorkers deserve strong public health protections that prevent disease outbreaks and save lives,” said Council Member Lynn Schulman, Chair of the Committee on Health. “The new cooling tower regulations taking effect today implement the legislation I was proud to champion last year following the Legionnaires’ flare-up in Central Harlem and establish a more rigorous testing schedule for Legionella bacteria citywide. More frequent testing will help buildings identify potential problems earlier and strengthen safeguards for tenants, workers, and surrounding communities. I thank Commissioner Dr. Alister Martin and the New York City Health Department for their partnership in advancing these important protections and their continued commitment to keeping New Yorkers safe.”