NEW YORK CITY LEGIONNAIRES' DISEASE CLUSTER GROWS ON UPPER EAST SIDE

New York City's Health Department is investigating a Legionnaires' disease cluster on Manhattan's Upper East Side. As of July 9, according to the city Health Department and local reporting, the cluster had grown to 46 cases, with 22 hospitalisations and no deaths reported. The count has been rising through the investigation, so those totals reflect the position as of July 9 rather than a current figure.

The investigation began on July 2, when initial cases were detected. Local reporting said the confirmed count increased through several updates before reaching 46 cases as of July 9. Cases have been concentrated in ZIP codes 10028, 10128 and 10075, covering parts of the Upper East Side including Yorkville and Carnegie Hill. The Health Department has been investigating environmental sources in that area rather than warning of a citywide water or household air-conditioning risk.

The Health Department said the likely source is a cooling tower in the area. Cooling towers can spray mist into the air, and that mist can carry Legionella bacteria if the tower is contaminated. Legionnaires' disease is a form of pneumonia contracted by breathing in mist containing Legionella bacteria. It does not spread from person to person, according to city health guidance.

As of July 6, according to city officials cited in local reporting, roughly 160 cooling towers were registered within the three ZIP codes under investigation, and Health Department staff had collected samples from 139 towers. As of July 10, the Health Department had identified 31 buildings where Legionella bacteria was detected, and 19 of those buildings had been disinfected. Testing and remediation work has continued since those dates.

Mayor Zohran Mamdani said the outbreak is not tied to building plumbing or indoor air-conditioning units, and that residents in the area can safely drink tap water, bathe, shower, cook and use home air conditioning. That guidance matters because Legionnaires' outbreaks can create confusion about whether household water or ordinary air conditioning is unsafe. The city's message is that the investigation is focused on cooling towers, not residential plumbing or window air-conditioning units.

Symptoms of Legionnaires' disease include fever, cough, shortness of breath and muscle aches, and city health guidance says symptoms can begin two to 14 days after exposure. People who live in or recently visited the affected Upper East Side area and develop pneumonia-like symptoms are advised to seek medical care and tell a provider about possible exposure. Older adults, people with weakened immune systems and people with chronic lung disease are generally at higher risk of serious illness.

The cluster comes after a larger Legionnaires' outbreak in Central Harlem last summer that sickened more than 100 people and killed seven. That history has raised scrutiny of how quickly the city identifies contaminated cooling towers and completes disinfection. The current investigation remains focused on identifying which cooling tower or towers contributed to the cases reported in the affected ZIP codes.

The next developments to watch are updated case counts from the Health Department, completion of disinfection at buildings where Legionella was detected, and any city finding that identifies a specific cooling tower as the outbreak source. For now, the dated public record is that the Upper East Side cluster had reached 46 cases as of July 9, with 22 hospitalisations, no deaths reported, and cooling towers under investigation.

Fact-check date: 12 July 2026
Article type: News
Sources: NY1; CBS New York; NBC New York; Fox 5 New York; ABC7 New York; NYC Health Department
Developing note: Case figures are dated July 9 and may have changed. Details may change as officials release information.