New York City Health Department Closes Investigation of Central Harlem Legionnaires’ Disease Cluster

New York City Health Department Closes Investigation of Central Harlem Legionnaires' Disease Cluster

Cluster Investigation is Complete and Residents and Visitors to Central Harlem Are Not at Increased Risk of Acquiring Legionnaires' Disease

Adams Administration Proposes Package of Reforms to Reduce Risk of Legionnaires

Molecular Analysis Matches Legionella Strain Found in Cooling Towers at Two Locations to Legionella Bacteria Found in Seven Patients in the Cluster.

August 29, 2025 - Today, the New York City Health Department announced that the Central Harlem community cluster of Legionnaires' disease has ended. The last day that New Yorkers who live or work in the area began feeling symptoms of Legionnaires' disease was August 9. As of yesterday, August 28, there have been 114 cases of Legionnaires' disease associated with this cluster; 90 people have been hospitalized; six remain hospitalized; and, unfortunately, seven people have died. In the Central Harlem cluster, at least 90 percent (104) of the people with Legionnaires' disease had a known risk factor for severe disease, including being age 50 years and above, people who smoke, people with chronic lung disease or chronic conditions, or having a compromised immune system. All facilities with cooling towers in the cluster area fully cooperated with the Health Department, and those with Legionella positive test results completed full cleaning and disinfection as directed.

"Today marks three weeks since someone with symptoms was identified, which means New Yorkers should be able to breathe a sigh of relief that residents and visitors to Central Harlem are no longer at an increased risk of contracting Legionnaires' disease - but our job here is not done," said New York City Mayor Eric Adams. "We must ensure that we learn from this and implement new steps to improve our detection and response to future clusters, because public safety is at the heart of everything we do, and we will never stop working to protect New Yorkers. This is an unfortunate tragedy for New York City and the people of Central Harlem as we mourn the seven people who lost their lives and pray for those who are still being treated. I am grateful to the frontline heroes at the New York City Health Department and Health + Hospitals, who undoubtedly saved many others."

"As the city's doctor, my thoughts are with everyone who has been impacted by the spread of Legionella, and our hearts are with the families who lost a loved one," said NYC Acting Health Commissioner Dr. Michelle Morse. "Thank you to the residents of Central Harlem, the elected officials, and community leaders who worked with the agency to keep New Yorkers informed. After an extensive investigation, we were able to identify two cooling towers that had a genetic match with patient specimens. We are working with building owners on next steps to protect the health and safety of Harlem residents and to prevent future clusters."

"Harlem Hospital faced a surge of patients and rose to the occasion, and I want to thank them for their long hours and deep commitment to their patients," said NYC Health + Hospitals President and CEO Mitchell Katz, MD. "I also want to recognize our Engineering team, who run a robust cooling tower maintenance program that exceeds requirements by the NYC Health Department, treating the cooling towers each day with chemicals to minimize harmful microbes. Thanks to them, we know that the cooling tower at Harlem tested negative for Legionella in March and June, and as part of routine maintenance, was fully disinfected on July 2, three weeks before the first case in the cluster. We are grateful to our partners at the NYC Health Department and City Hall for their support."

New York City has among the most rigorous and protective laws and regulations in the country that aim to reduce the risk of Legionnaires' disease from cooling towers. Building owners with cooling towers are required to implement steps, including but not limited to registering the cooling tower, developing and implementing an operating protocol, and monitoring water quality at least three times a week. Health Department scientists (water ecologists) conduct inspections to promote compliance with these requirements.

Today, the Adams administration is proposing a package of resources and policy changes to further reduce the risk of future clusters. These proposals include:

• Expanding the Health Department's capacity to inspect the city's cooling towers, including hiring additional water ecologists to conduct inspections and building system engineers to assess building mechanical systems and plumbing.
• Requiring building owners to test for Legionella at least every 30 days during the cooling tower operating period instead of the current 90-day requirement.
• Expanding the Health Department's sampling capacity to conduct proactive sampling of building cooling tower systems and maintain contracts to surge capacity when faced with novel issues during future clusters.
• Increasing fines for violations for failure to comply with cooling tower local laws and regulations.
• Requiring the Health Department and other involved city agencies to conduct a full review of the city's cooling tower rules to further strengthen oversight.
• Establishing a community engagement team staffed by community health workers based in the Health Department's neighborhood health action centers to be rapidly deployed to provide information and education to neighborhood residents during an emergency and focus on improving the health of New Yorkers year-round.

In addition to these proposals, the Health Department is undergoing a full review of the city's cooling tower rules to further strengthen city regulations.

After extensive investigation that included cutting-edge molecular analysis of Legionella bacteria from human and cooling tower specimens, the Health Department's Public Health Laboratory matched the Legionella strain found in cooling towers located at two locations: NYC Health + Hospitals/Harlem (Harlem Hospital), located at 506 Lenox Avenue, and a nearby construction site overseen by NYC Economic Development Corporation (NYCEDC) and construction contractor Skanska USA located at 40 West 137th Street with the strain found in seven patients. The Health Department received seven clinical specimens in this cluster. The Health Department typically receives culture specimens for 6-9% of all reported cases of Legionnaires' disease.

On July 25, the day the investigation began, the Health Department sampled the Harlem Hospital cooling towers. On July 30, Harlem Hospital disinfected the cooling tower. Also on July 30, the Health Department inspected the cooling tower as part of the cluster investigation and found it to be in full compliance with regulations. On August 7, after the Health Department's sample came back positive on the culture test, Harlem Hospital drained, disinfected, and refilled the cooling tower.

Skanska USA is currently managing the construction at 40 West 137th Street. The Health Department sampled the cooling tower on July 28, which showed a positive polymerase chain reaction (PCR) test, and the construction contractor completed a full remediation on August 1.

Both buildings have complied with all directives from the Health Department and are working with the Health Department on their long-term management programs.

Legionnaires' disease is a type of pneumonia that is caused by the bacteria Legionella, which grows in warm, stagnant water. Symptoms resemble other types of pneumonia and can include fever, chills, muscle aches, and cough. In some cases, Legionnaires' disease can be traced to contaminated water systems, particularly where conditions favor the growth of Legionella, such as cooling towers. People can get sick by breathing in water vapor containing Legionella bacteria, which may be emitted by cooling towers. It is not transmitted from person to person. Legionnaires' disease is not caused by drinking water. During a community cluster, the elevated risk from a contaminated cooling tower is to the surrounding neighborhood.

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