A fourth person has died in a legionnaires' disease outbreak in New York City, health officials said Monday, expressing confidence that the source of exposure has likely been eliminated.
The city's health department reported that the outbreak, traced to cooling towers in Manhattan's Upper East Side, has sickened 76 people. Of those, 53 have been discharged after hospital treatment, and 12 are recovering at home.
Outbreak Timeline and Response
A graph accompanying the press release showed the most recent diagnosis was on 15 July, with the peak a week earlier when 13 infections were confirmed. Health Commissioner Dr Alister Martin said on X: 'At this time, we believe any source of exposure has likely been eliminated. We have not seen anyone with new symptoms in over a week. We are focused on inspecting every cooling tower that tested positive and enforcing our laws to their fullest extent.'
Authorities did not release details about the fourth victim. Martin said: 'We mourn their passing, and our thoughts are with their family and loved ones.'
Disease and Source
Legionnaires' disease is a serious form of pneumonia, treatable but killing about 10% of patients, according to the US Centers for Disease Control and Prevention. The Legionella bacterium grows in warm water and can proliferate in cooling towers, hot tubs and showerheads.
Health officials believe the source was buildings in the Upper East Side neighborhoods of Carnegie Hill and Yorkville. In total, 76 buildings tested positive for living or dead Legionella bacteria in cooling towers, including museums, private schools and apartment houses. Owners were ordered to drain and sanitize cooling systems.
The health department said: 'This is not an issue with any building's plumbing system. Residents can continue to drink tap water, bathe, shower, cook, and use your air conditioner at home. Any New Yorkers who currently live or work in this area or people who have visited the area since late June and are experiencing flu-like symptoms, such as cough, fever, or difficulty breathing should contact a health care provider immediately.'
People contract the disease by inhaling tiny droplets of contaminated water; it does not spread person to person.
Previous Outbreak and Official Remarks
A previous outbreak in Harlem in August 2025 killed seven people and sickened more than 100. That episode followed a similar pattern, with cases trailing off after the source was identified and eliminated, and officials declared it over after about three weeks.
New York Mayor Zohran Mamdani addressed the outbreak at a small business event Monday, saying: 'I'm heartbroken by the loss of our fellow New Yorkers and send my deepest condolences to their loved ones.' He said city officials began tracking the outbreak on 2 July after two confirmed cases. 'Following the guidance of public health experts, we directed every building with an initial positive test result to immediately clean and disinfect its cooling tower. Due to the aggressive strategy of early testing, enforcement and remediation, we believe that we have now eliminated the source of exposure. We are continuing to inspect cooling towers and will aggressively enforce our public health laws.'
