What to know about the Legionnaires' disease outbreak in NYC

New York City health officials are investigating a Legionnaires' disease cluster on Manhattan's Upper East Side, centered on Carnegie Hill and Yorkville, as they work to identify and disinfect the source.

As of the city’s latest update, 36 cases had been confirmed and 22 people had been hospitalized. Officials said no deaths had been reported.

The health department said the likely source is contaminated cooling towers, which are being tested and disinfected. Officials also said the outbreak is being tracked across the area and that people who were in the affected neighborhoods and later develop symptoms should seek medical care.

What officials have said

The cluster was first identified after a small number of cases were reported in early July. Reporting later showed the count rising quickly, from 2 cases to at least 18, then into the low 20s. The city then updated the tally again, saying the outbreak had reached 36 confirmed cases and 22 hospitalizations.

The neighborhoods named in coverage include Carnegie Hill and Yorkville, and reports identified ZIP codes 10028, 10128 and 10075 as part of the affected area.

Why cooling towers matter

Legionnaires' disease is a severe form of pneumonia caused by Legionella bacteria. It is typically contracted by breathing in contaminated water droplets from sources such as cooling towers, hot tubs or showerheads.

City officials said there is no risk from tap water or air conditioners, and the disease does not spread person-to-person.

Who is most at risk

Older adults and people with weakened immune systems are at higher risk of serious illness. Public health guidance says anyone who was in the affected area and develops flu-like symptoms should get evaluated, especially if the symptoms include fever, cough or shortness of breath.

Why this outbreak is getting attention

The rapid rise in reported cases has put pressure on the city to find and disinfect the source quickly. It has also renewed attention on cooling-tower oversight in New York City, where a Legionnaires' outbreak in Harlem in 2025 already raised concern about public health monitoring.

Officials are expected to continue testing and disinfecting cooling towers in the affected area and to keep updating case counts as the investigation continues.