NYC health officials map Upper East Side cooling towers amid Legionnaires' outbreak
City data show 55% of 203 cooling towers in the affected Upper East Side ZIP codes reported Legionella test results in 2026, while about half have not been inspected in over a year.
New York City health officials are expanding their investigation of a Legionnaires’ disease cluster on the Upper East Side. Mayor Zohran Mamdani said the city will publish the locations of any cooling towers that test positive for Legionella as soon as results are available.
An analysis of registration records identified 203 active cooling towers in the three ZIP codes that include Carnegie Hill and Yorkville, compared with the 160 towers the health department has listed for the same area. The discrepancy was not addressed by a department spokesperson.
City law, effective May, requires owners to test towers for Legionella and report results monthly; before that, testing was required quarterly. Owners must also maintain detailed plans to prevent contamination. Health officials aim to inspect each of the city’s roughly 5,000 towers at least once a year, but staffing shortages have limited progress.
Public data indicate that 55% of the Upper East Side towers had test results on file for 2026, a compliance rate slightly below the citywide average. Approximately 50% of towers in the area have not been inspected in more than a year, mirroring the citywide inspection gap.
"Ask them why the record is incomplete," microbiologist Janet Stout, a Legionella specialist, advised residents, adding that the presence or absence of recent test results does not necessarily increase individual risk.
Stout explained that Legionella spreads through water mist emitted by towers and can travel considerable distances, so risk is not confined to a single tower. She cautioned that the rapid PCR tests used by the city detect both live and dead bacteria, meaning a positive result does not automatically indicate an active source of infection.
Health officials urged anyone who visited the neighborhoods in recent weeks and is experiencing flu-like symptoms, especially elderly or immunocompromised individuals, to seek medical care promptly. Carnegie Hill has a higher proportion of residents aged 65 or older (29%) than the citywide average (15%).
As of Wednesday, 36 people in the affected neighborhoods had been diagnosed with Legionnaires’ disease, and 22 were hospitalized. Towers that test positive will be required to be drained, cleaned and disinfected.