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Legionnaires' disease hits Central Harlem. Here's what to know about the outbreak.
By
Caroline Lewis
Published Aug 5, 2025
Modified Aug 22, 2025
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BSIP/UIG Via Getty Images
By
Caroline Lewis
Published Aug 5, 2025
Modified Aug 22, 2025
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Six people have died and 112 have been sickened in the Legionnaires’ disease outbreak in Central Harlem, the New York City Health Department reported Friday, Aug. 22. Seven people remain hospitalized.
Legionnaires' disease typically spreads when people inhale mist containing Legionella bacteria, which can grow in buildings’ water-cooling tanks, making it a longtime scourge for New York City.
City health officials say they have taken steps to control the outbreak but are still urging anyone experiencing the flu-like symptoms associated with Legionnaires’ disease to seek medical treatment. The current outbreak is affecting ZIP codes 10027, 10030, 10035, 10037 and 10039 and the surrounding areas.
Here’s what you need to know now about Legionnaires’ disease, who’s most at risk and what the city is doing to prevent more people from getting sick.
What is Legionnaires’ disease and how does it spread?
Legionnaires’ disease is a form of pneumonia that first emerged in Philadelphia in 1976 in an outbreak affecting attendees of an American Legion convention, according to the U.S. Centers for Disease Control and Prevention.
The disease is not spread from person to person, according to the CDC. Instead it’s typically spread by inhaling mist containing Legionella bacteria, which can grow in water systems such as cooling towers, hot tubs and plumbing systems. Typically, Legionella grows in water that’s warm, stagnant or doesn’t contain enough disinfectant, according to the CDC.
Window air conditioners are not a source of Legionnaires’ disease, the CDC adds.
In New York City,hundreds of cases of Legionnaires’ disease have been reported each year for the past decade and cooling towers have become a particular source of concern. They are linked to both the current outbreak and major outbreaks that originated in the Bronx in 2015 and at Amsterdam Nursing Home in Upper Manhattan in 2022.
City officials have emphasized that the current outbreak in Harlem is not tied to issues with buildings’ plumbing systems, so people in the area can safely drink tap water, use their air conditioners, shower and cook as usual.
What are the symptoms of Legionnaires’ and who’s most at risk?
Not everyone who is exposed to Legionella bacteria develops symptoms and most people are at low risk for the disease, according to city health officials. Symptoms are typically similar to those associated with the flu. They can include cough, fever, chills, muscle aches and difficulty breathing, according to the city health department. They can also include headaches, fatigue, loss of appetite, confusion or diarrhea.
About 1 in 10 people diagnosed with Legionnaires’ dies from complications of the disease, according to the CDC.
People who are over 50, smoke or have chronic lung disease or weakened immune systems are at higher risk for severe disease, according to the city health department.
What should you do if you feel sick?
New Yorkers with flu-like symptoms should seek medical attention so they can be tested and treated for Legionnaires’ disease, especially if they’re in a high-risk group, according to acting city Health Commissioner Dr. Michelle Morse. Treatment, which may include antibiotics, is particularly effective if the disease is caught early, Morse said.
Can Legionnaires’ disease be prevented?
There’s no vaccine for Legionnaires’, but local lawmakers have taken steps in recent years to try to ensure better maintenance of water cooling towers. After a 2015 outbreak in the Bronx that resulted in 138 cases and 16 deaths, the City Council passed legislation requiring every water cooling tower to be registered with the city and requiring the city to track cooling tower inspections and violations.
The number of Legionnaires’ cases reported annually in the city has fluctuated since then. In 2018, more than 600 cases were reported. Last year, there were 257, according to a preliminary count from the health department.
According to the city health department, when two or more cases of Legionnaires’ are confirmed within a 12-month period that are associated with a particular residential building with a shared hot water system, the city mandates an evaluation of the building’s water system and orders the building owner to notify residents and staff.
How can I learn more about the water in my own building?
Building owners in the city are required to register cooling towers and test the water at least every 90 days for the presence of the Legionella bacteria. You can check online for results of Health Department inspections of cooling tower systems by building address or building identification number (BIN).
What is the city doing to contain the current outbreak?
After the city noticed a cluster of Legionnaires’ cases emerging in Harlem last month, officials screened all water cooling towers in the area for Legionella bacteria, according to the city health department. The city said on Thursday, Aug.14, 12 cooling towers at 10 sites tested positive for Legionella bacteria, some of them housing government operations. All 12 towers had been cleaned or remediated as of Friday, Aug. 15, according to the city.
Chantal Gomez, a spokesperson for the city health department, said earlier that officials expect that an initial remediation of the sites will prevent more people in the area from getting sick. But, she said, it’s likely more cases will be reported before the outbreak is over because the incubation period for Legionnaires’ can delay symptoms by several days.
What are the outstanding questions about the current outbreak?
The city has not released information on the people who have died from Legionnaires’ in the current outbreak, including their ages or whether they had underlying health conditions.
According to the city health department, public health lab experts are still working to identify, through DNA sequencing, which specific building or buildings caused the current cluster of Legionnaires’ cases. The officials say those facilities will undergo more thorough remediation once they’re identified.
This story was updated Aug. 22 with additional information.
Tagged
Health and Science
Legionnaires disease
harlem
Caroline Lewis
Caroline Lewis is on the health care beat for WNYC and Gothamist. She has covered COVID, a nurses' strike, the overdose crisis and New York’s marijuana legalization effort, and spent a year investigating patients' medical bills. She always wants to hear about how everyday New Yorkers experience the health system. Got a tip? Email [email protected].
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Gothamist is funded by sponsors and member donations
Gothamist is funded by sponsors and member donations
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