NYC health officials investigate source of Upper East Side Legionnaires' outbreak

New York City health officials have confirmed 36 cases of Legionnaires' disease associated with cooling towers in three Upper East Side ZIP codes covering Carnegie Hill, Yorkville and Lenox Hill. Twenty-two of the patients are hospitalized. The department says the bacteria are spread through contaminated mist from external cooling towers, not from indoor plumbing, and residents can continue to use tap water and home air-conditioning systems.

"It's important to understand the risk here isn't coming from inside the building, it is coming from outside the building in these ZIP codes," said ABC News correspondent Dr. Darien Sutton.

Mayor Zohran Mamdani announced that the city will soon publish the addresses of buildings where legionella has been detected, emphasizing transparency for residents. Testing of the cooling towers is expected to finish by the end of Wednesday, after which a list of towers of interest will be released by week’s end. Officials warned that pinpointing the exact source may take weeks.

"We're going to be taking the step of releasing the addresses of wherever has been impacted, because we know that transparency is also a critical part of how New Yorkers can continue to go about their day," Mamdani said.

Health officials reminded the public that Legionnaires' disease is not transmitted person-to-person and that most healthy individuals will not become ill, though about one in ten infected persons face a risk of death, particularly the elderly, smokers and those with underlying health conditions. They urged anyone with flu-like or pneumonia symptoms to seek medical care, noting that case numbers are likely to rise as testing continues.