Legionnaires’ Disease Outbreak Investigation in Upper East Side

In a troubling development, over half of the water cooling towers on the Upper East Side that are under scrutiny for a recent outbreak of Legionnaires’ disease were discovered to be dirty after an inspection by health officials.

Between March 2025 and March 2026, records indicate that 59% of cooling centers in the affected three ZIP codes had violations. These included failures to conduct regular maintenance and cleaning, as well as not submitting mandatory legionella test results to the health department.

Notably, the Carnegie Hill and Yorkville areas saw the highest incidence of violations. For instance, 1520 York Avenue recorded nine violations, while 1101 Lexington Avenue tallied seven. Both locations had issues related to cleaning, surveillance, chemical treatments, and Legionella sampling back in February.

Additionally, eight cooling towers in the affected area had not collected or submitted legionella samples as required since March 2025. These locations include various addresses on East 86th and 87th Streets, York Avenue, and Madison Avenue.

In total, more than 200 cooling towers citywide were flagged for violations, including 70 related to Legionella bacteria during the same timeframe.

A city health department official emphasized the importance of enforcing regulations, stating fines can range from $500 to $2,000 for repeat offenders. However, it’s crucial now to test all relevant towers and remediate them if they show Legionella contamination, whether live or dead.

The current outbreak was first reported on July 2 and has already affected 36 individuals in the ZIP codes 10028, 10128, and 10075. With ongoing investigations, further testing could potentially reveal more cases. This outbreak follows a severe incident in Harlem last summer, which resulted in seven fatalities and 114 illnesses.

The scope of this year’s investigation is expected to be more extensive due to the presence of three times as many cooling towers in the area compared to Harlem. New legislation effective since May mandates monthly testing for Legionella in cooling towers, replacing the former quarterly requirement. Yet, only about half of the active towers in the affected Upper East Side ZIP codes have shown positive results for Legionella this year.

As of Thursday, health officials reported that nearly all cooling towers in the area have been tested, with results coming in progressively. The mayor’s office has also committed to publicizing the addresses of buildings that test positive for Legionella.

One cooling tower at 1511 Third Avenue has already tested positive for bacteria. This tower has a history of numerous violations and was last inspected in December 2024, despite city officials aiming for annual inspections.

Towers that have previously tested positive must be drained and disinfected. Inspectors will also analyze the DNA sequence of the Legionella bacteria found in these towers and compare it with samples from affected individuals.

Concerns were voiced by New York City Council President Julie Menin, who represents the Upper East Side. Speaking at a recent event, she expressed her worry about the ongoing investigation and its implications for the densely populated area, which has a significant elderly demographic.

Menin has urged the health commissioner to prioritize aggressive disinfection in buildings that have yet to be tested or where infected individuals have not yet cleared the bacteria. In her view, delaying action could lead to more illnesses or fatalities.

“Every day that goes by without disinfecting increases the risk of people getting sick and potentially dying,” she said. “This is completely unacceptable.”