Legionnaires' disease outbreak in New York City's Upper East Side grows to at least 28 cases

New York City health officials are investigating a Legionnaires' disease outbreak on the Upper East Side that has sickened at least 28 people and triggered citywide cooling-tower testing.

The cluster is centered in Carnegie Hill and Yorkville, including ZIP codes 10028, 10128 and 10075. Officials say the probable source is contaminated cooling towers, and they are urging residents with flu-like symptoms to seek medical care.

AP first reported the outbreak on July 6, when the city said there were 23 reported cases, 17 hospitalizations and no deaths at that time. Subsequent reporting has put the count higher, showing how quickly the investigation is still moving.

What the city knows

Legionnaires' disease is a serious form of pneumonia caused by Legionella bacteria. It is commonly associated with inhaling contaminated water droplets from sources such as cooling towers, which can release fine mist into the air.

City officials say the disease is not spread person-to-person. They also say there is no risk from tap water or air conditioners, a point they have repeated as they try to reassure residents living near the affected buildings.

The city has been testing cooling towers across Manhattan and beyond as part of the response. Later reporting said roughly 160 buildings had been tested and disinfection had been ordered at 19 sites.

How the outbreak developed

The first major public update came on July 6, when AP reported the cluster on the Upper East Side with 23 cases and 17 hospitalizations. At that point, officials had not reported any deaths.

By July 8, the New York Post reported at least 36 confirmed cases and 22 hospitalizations, along with city review of calls for immediate cooling-tower disinfection. On July 9, The Guardian reported at least 28 people sickened, along with broader testing and disinfection activity.

Those differing counts reflect a fast-moving public-health investigation rather than a settled final tally. Officials are still matching laboratory results, hospital reports and environmental testing as the city works through the affected area.

Response and risk

Council Speaker Julie Menin has called for broader and immediate cooling-tower disinfection. Reporting on July 8 said the city was reviewing that request while inspectors continued identifying and disinfecting towers contaminated with Legionella.

The outbreak matters because it is unfolding in a dense residential part of Manhattan with many multiunit buildings and shared water systems. In that setting, speed is critical: the longer a contaminated cooling tower remains active, the more people may be exposed.

Older adults and people with weakened immune systems face the highest risk of severe illness. Health officials are focusing on symptom awareness for anyone who develops fever, cough, muscle aches or other flu-like signs after possible exposure.

What remains unknown

Officials have not publicly identified a single source building or tower. It is also not yet clear whether the case count will keep rising, whether additional hospitalizations will be reported or whether any deaths will be linked to the outbreak.

For now, the immediate next steps are continued testing, targeted disinfection and further city updates as environmental and clinical results come in. The outbreak remains under investigation, and the official total may change again.