What to know about the severe pneumonia cluster on NYC’s Upper East Side

On the Upper East Side of New York, some residents on Monday were just learning that a cluster of Legionnaires’ disease, a severe form of bacterial pneumonia, had formed in the Manhattan neighborhood they call home.

“Is this the location where the Legionnaires’ is breaking out? Oh my gosh,” said Charlie Miller as he covered his face with his shirt.

The New York City Department of Health and Mental Hygiene said 23 people have fallen ill from the bacteria, 17 of whom have been hospitalized. The Health Department had previously said those infected were in ZIP codes 10028, 10128 and 10075.

Now the east side of Central Park from 76th Street to 97th Street is in the affected zone, as well. Because of the expanded zone, some believe they or someone they know may have had the illness without ever even considering it a possibility.

“We go to Central Park on 79th, we enter the park that way. And I’m like, this is so mysteriously the same symptoms that she had, because it was probably like two to three weeks of coughing,” Matt Sheldon said about his wife, who experienced the symptoms a couple of weeks ago.

Health Department officials held a virtual town hall meeting Monday night to address questions and concerns. While the source of the Legionella bacteria has not yet been identified, the department said it’s focused on cooling towers.

“Over 160 cooling towers across this specific region that we’re looking at, and we are not waiting. The work has already begun in terms of remediating,” said NYC Health Commissioner Dr. Alister Martin.

Legionella typically develops in cooling towers that haven’t been cleaned frequently enough. Once the bacteria form, they drift into the air through water vapor. It cannot be transmitted person to person. Over the summer of 2025, seven people died during a Legionnaires’ cluster in Harlem.

The New York City Council changed the law mandating that buildings be tested and cleaned and that reports must be filed with the Health Department every 90 days, but the law has been in effect only since May. City Council Speaker Julie Menin said she has questions.

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“Is the Health Department focusing on those buildings that were not compliant? Because obviously we’re deeply concerned that the source of this outbreak has not yet been identified,” the speaker said.

The Health Department recommended people in the affected area stay away from steam while indoors. In terms of what to look out for, the Health Department said to watch for flu-like symptoms, including cough, fever and difficulty breathing — and then to go straight to the doctor to get tested.

Drinking water, cooking, showering and using air conditioning are typically safe.

But the best thing to do is look out for flu-like symptoms, including cough, fever and difficulty breathing — then go straight to the doctor to get tested.

All buildings with cooling towers are being instructed to immediately clean and test for Legionella bacteria. But because it takes a few days for Legionnaires’ disease to develop in humans, more cases may be discovered before things settle down.