Fourth Death Confirmed in NYC Legionnaires’ Disease Outbreak
A fourth person has died in connection with a Legionnaires’ disease outbreak on Manhattan’s Upper East Side, city health officials confirmed Monday, even as Mayor Zohran Mamdani announced that the source of the bacterial infection appears to have been eliminated. The outbreak, which began in late June, has sickened 76 people across three ZIP codes in the Carnegie Hill and Yorkville neighborhoods, according to NBC News.
The Outbreak by the Numbers
As of Monday evening, the New York City Health Department had confirmed 76 total cases, with seven patients still hospitalized and 53 discharged. The fourth death marked the fourth consecutive day a fatality had been reported — the first was announced on Friday, July 17, followed by additional deaths on Saturday, Sunday, and Monday. Health officials say no new cases have been diagnosed since July 15, and no one has developed new symptoms in more than a week.
Source Investigation and Response
The Health Department identified 31 cooling towers that tested positive for Legionella pneumophila bacteria within the affected area. All 76 buildings ordered to clean and disinfect their cooling towers have complied, according to officials. The bacteria, which causes a severe form of pneumonia, thrives in warm, stagnant water and is typically found in large building air conditioning systems, hot tubs, and decorative fountains.
“We believe we have now eliminated the source of exposure,” Mayor Mamdani said in a statement. “Regardless, we will continue to inspect cooling towers and aggressively enforce health laws. I’m heartbroken by the loss of my fellow New Yorkers and send my deepest condolences to their loved ones.”
The mayor also reassured residents that tap water remains safe, saying, “I want to reassure New Yorkers they can use tap water, bathe, shower and cook and use air conditioners at home.”
Health Commissioner Dr. Alister Martin echoed that assessment, writing on social media that “any source of exposure has likely been eliminated” and that the department is “focused on inspecting every cooling tower that tested positive and enforcing our laws to their fullest extent,” as NY1 reported.
Human Toll
Among the deceased is an 88-year-old military veteran who spent two weeks in the intensive care unit before dying. His attorney, Ronald Katter, described the sudden onset of illness: “It wasn’t as if he has an acute illness that he was suffering for. He was sitting in his apartment by an open window and reading a magazine, and when she came home, he had a 104-degree fever.”
Katter, who represents the victim’s widow and other affected families, said they are awaiting the completion of the investigation to identify the responsible cooling tower owner. “We’re waiting for the investigation to be completed to identify the responsible cooling tower owner,” Katter said, noting that the man’s own apartment building tested negative and was not among those ordered to disinfect.
Understanding Legionnaires’ Disease
Legionnaires’ disease is a severe form of pneumonia caused by Legionella pneumophila bacteria. The disease is contracted by inhaling tiny droplets of contaminated water — it is not contagious and cannot spread from person to person. According to the U.S. Centers for Disease Control and Prevention, the disease is treatable but kills approximately 10% of those infected. People over 50, smokers, and those with chronic lung disease or weakened immune systems face the highest risk.
A Recurring Challenge for New York City
This outbreak follows a larger Legionnaires’ cluster in Central Harlem in 2025, which killed seven people and sickened more than 100. That outbreak was declared over on August 29, 2025, after two city buildings were identified as the sources, as NY1 reported. The current Upper East Side outbreak appears to be following a similar containment pattern through aggressive cooling tower testing and disinfection.
What’s Next
Health officials continue to investigate the exact source of the outbreak, a process that could take weeks. The Health Department advises anyone who has spent time in the affected ZIP codes — 10028, 10075, and 10128 — to seek medical attention if they develop flu-like symptoms, as symptoms can appear up to 14 days after exposure.
Attorney Ronald Katter indicated that civil litigation against building owners may follow once the investigation identifies which cooling tower or towers were responsible. “They’re looking to be made whole from the suffering they’ve experienced,” Katter said, as The Guardian reported.
Mayor Mamdani has promised aggressive enforcement of health laws regarding cooling tower maintenance, signaling potential policy changes to prevent future outbreaks. With summer conditions ideal for Legionella growth, city officials are urging building owners to remain vigilant in maintaining their cooling systems.