NYC Health Officials Report Three Deaths in Legionnaires’ Disease Cluster

The New York City Health Department has reported that three people have died in connection with the Legionnaires’ disease community cluster on the Upper East Side as of July 19.

At the same time, NYC health department data continues to show a sustained decline in newly diagnosed cases, indicating that the source of exposure to Legionella bacteria has likely been eliminated.

As of July 19, the health department has identified 74 cases of Legionnaires’ disease associated with the cluster. Nine people remain hospitalized, 50 have been discharged from the hospital, and three people have died. From July 10 through July 17, the health department confirmed an average of fewer than one new case per day. During the first week of the investigation, from July 2 through July 8, the health department confirmed an average of more than eight new cases per day. These figures may change as new cases are investigated and confirmed.

“Our aggressive strategy of testing, enforcement, and remediation appears to have stopped the source of exposure,” said Dr. Alister F. Martin, NYC health commissioner.  We directed every building with an initial positive test result to immediately clean and disinfect its cooling tower, and everyone has completed that work. We have also reminded cooling tower operators across the city of their summertime requirement to increase use of biocides that kill Legionella bacteria. We will continue inspecting every cooling tower that tested positive and will hold accountable any owner who fails to comply with our public health laws.”

Case investigations also show a sharp decline in illnesses beginning after July 8. People whose cases have only recently been confirmed began experiencing symptoms more than a week ago, indicating that there has not been recent exposure. The health department is also not seeing concerning trends in hospital emergency department data, which can identify potential cases before they are formally diagnosed.

On July 14, the health department ordered 76 buildings with cooling towers that returned positive initial polymerase chain reaction (PCR) screening results to clean and disinfect their systems as part of the Upper East Side investigation. By July 16, all 76 confirmed they completed the required remediation.

As CMM previously reported, this was the first time NYC has taken this approach. In previous community cluster investigations, buildings with positive PCR results were initially required to boost chemical disinfectant levels while awaiting confirmatory culture testing, a process that can take up to two weeks. Full cleaning and disinfection was generally required only after a positive culture result.

In total, the health department collected samples from 183 cooling tower systems across the affected area and has completed all initial PCR screening tests for Legionella bacteria. No PCR test results are outstanding.

NYC has some of the nation’s strongest laws governing cooling tower maintenance and Legionella prevention. Building owners are required to properly maintain cooling towers and regularly monitor them for bacterial growth, and the health department enforces those requirements.

To promote compliance, the health department aims to inspect every registered cooling tower each year. During the first six months of 2026, inspectors completed nearly 1,600 cooling tower inspections, a 35% increase over the same period in 2025.

When inspectors identify violations, the health department issues summonses and may impose financial penalties. In Fiscal Year 2025, the health department collected approximately US$680,000 in cooling tower-related fines and issued 1,337 violations, including:

• 253 public health hazards
• 810 critical violations
• 274 general violations

In May, health department regulations took effect requiring cooling tower operators to test for Legionella every 31 days while systems are operating—three times more frequently than previously required. Operators must submit testing information to the health department after each test.

Although the requirement has been in place for two months, compliance has been strong. Citywide, 77% of operators have already submitted the required testing information. Some cooling towers that have not yet reported may not currently be operating or may not yet have started seasonal operations. Compliance is verified during annual inspections, and failure to comply may result in enforcement action and fines.