A fourth person has died in New York City’s legionnaires’ disease outbreak, city health officials said Monday, as the number of confirmed illnesses linked to the Upper East Side cluster rose to 76.
The New York City Department of Health said the outbreak has been traced to contaminated cooling towers in buildings in the Carnegie Hill and Yorkville areas of Manhattan. Officials said 53 people have been discharged after hospital treatment, while 12 others are recovering at home.
Health Commissioner Dr. Alister Martin said the city believes the source of exposure has likely been eliminated, noting that officials have not seen anyone develop new symptoms in more than a week.
“At this time, we believe any source of exposure has likely been eliminated,” Martin said in a public update. He added that the city is continuing to inspect cooling towers that tested positive and enforce health regulations.
TRENDING TODAY
Officials did not release details about the fourth person who died. As with the earlier deaths, the city has not publicly identified the victims or provided additional personal information.
Legionnaires’ disease is a serious type of pneumonia caused by Legionella bacteria. The bacteria can grow in warm water systems, including cooling towers, hot tubs, fountains, large plumbing systems and showerheads. People can become sick when they inhale small droplets of contaminated water.
The disease does not spread from person to person. City officials stressed that the outbreak is not connected to household tap water or building plumbing systems.
Residents in the affected area can continue to drink tap water, cook, bathe, shower and use home air conditioning, according to the health department.
The outbreak was connected to cooling towers, which are part of large building heating and cooling systems. These systems can release mist into the air, potentially exposing people nearby if Legionella bacteria are present.
The city said 76 buildings tested positive for either live or dead Legionella bacteria in their cooling towers. The affected properties reportedly included apartment buildings, museums, private schools and other large facilities. Owners were ordered to drain, clean and disinfect the systems.
Health officials said the most recent diagnosis connected to the cluster was on July 15. The outbreak appeared to peak about a week earlier, when 13 infections were confirmed in one day.
Mayor Zohran Mamdani said the city began tracking the outbreak on July 2 after two confirmed cases and moved quickly to test, inspect and require cleaning of cooling towers with positive results.
“I’m heartbroken by the loss of our fellow New Yorkers and send my deepest condolences to their loved ones,” Mamdani said Monday.
Legionnaires’ disease can cause cough, fever, shortness of breath, muscle aches and fatigue. It is treatable with antibiotics, but it can become severe, especially for older adults, smokers, people with weakened immune systems and those with chronic lung disease or other underlying health conditions.
The U.S. Centers for Disease Control and Prevention says about one in 10 people who become sick with legionnaires’ disease die from complications. The risk can be higher among people who contract the disease in health care settings or who already have serious medical conditions.
City officials are urging anyone who lives, works or recently visited the affected Upper East Side area and is experiencing flu-like symptoms, cough, fever or breathing difficulty to contact a health care provider immediately.
The current outbreak follows another deadly legionnaires’ cluster in Harlem in 2025, which killed seven people and sickened more than 100. In that case, officials also said infections declined after the source was identified and remediated.
The latest outbreak may renew scrutiny of how New York monitors cooling towers, especially during warmer months when bacteria can grow more easily. Large buildings are required to maintain and test cooling towers, but outbreaks have continued to occur despite existing rules.
Public health experts have warned that aging infrastructure, warmer temperatures and inconsistent maintenance can increase the risk of Legionella growth in urban water systems.
Why It Matters
The outbreak shows how building systems that most residents never see can create serious public health risks when not properly maintained. Cooling towers are essential for large buildings, but they require regular testing, cleaning and enforcement.
For New Yorkers, the key message is caution without panic. The disease does not spread between people, and city officials say tap water and home air conditioning remain safe. But anyone with symptoms after time in the affected area should seek medical care quickly.
What Comes Next
New York health officials will continue inspecting cooling towers that tested positive and enforcing cleanup orders against building owners.
The city is also expected to monitor new diagnoses closely to confirm whether the outbreak is truly ending. If no additional cases appear, officials may later declare the cluster over.
NYC health officials say new legionnaires’ cases have slowed as they continue monitoring the Upper East Side cluster.
Our data continue to show a sustained decline in newly diagnosed cases of Legionnaires’ disease on the Upper East Side, indicating that the source of exposure to Legionella bacteria has likely been eliminated.
Learn more: https://t.co/0rXv78p1V1 pic.twitter.com/HOU8d1eA79
— nychealthy (@nycHealthy) July 20, 2026
