A growing outbreak of Legionnaires’ disease in New York City has now been linked to at least three deaths and more than 60 confirmed cases since late July 2025. The New York City Department of Health says the illness is concentrated in Central Harlem, affecting residents in several ZIP codes, including 10027, 10030, 10035, 10037, and 10039.
Officials have traced the outbreak to 11 contaminated cooling towers in the area. These are part of large building air conditioning systems that use water for cooling. When not properly treated, they can become breeding grounds for Legionella pneumophila, the bacteria that cause Legionnaires’ disease. Once the bacteria are in the water, tiny droplets can be released into the air and inhaled, leading to infection.
What Is Legionnaires’ Disease?
Legionnaires’ disease is a serious form of pneumonia — a lung infection — caused by breathing in water vapor contaminated with Legionella bacteria. You cannot catch it from another person, and it is not spread by drinking tap water. Instead, exposure comes from inhaling fine mist from contaminated water sources, such as:
- Cooling towers in large buildings
- Hot tubs and spas
- Decorative fountains
- Showerheads and plumbing systems in certain large facilities
Most healthy people who are exposed will not get sick. But in some cases, especially in older adults, smokers, or those with weakened immune systems, the bacteria can cause a dangerous lung infection that may require hospitalization.
Why This Outbreak Is Happening Now
According to infectious disease experts, Legionella bacteria thrive in warm, stagnant water, which is more common in summer months. In large building cooling towers, warm water can circulate if not properly treated with disinfectants. Even well-maintained systems can sometimes harbor the bacteria.
When cooling systems operate, they can release tiny water droplets into the air. Anyone nearby can breathe them in without realizing it. If the water is contaminated, those droplets can carry the bacteria deep into the lungs, causing infection.
In this case, health inspectors identified 11 cooling towers in Central Harlem with Legionella contamination. These systems have since been cleaned and treated, but experts warn that exposure could still occur until all systems are fully cleared and maintained.
Symptoms to Watch For
Legionnaires’ disease usually develops 2 to 14 days after exposure. Early symptoms can look like the flu, which makes it harder to recognize without medical testing. Key symptoms include:
- Cough, often persistent and worsening
- Fever and chills
- Shortness of breath
- Muscle aches
- Headache
- Fatigue
In severe cases, the infection can cause lung failure or spread to other parts of the body. Without prompt treatment, the illness can be fatal — particularly for vulnerable individuals.
Who Is Most at Risk?
While anyone can get Legionnaires’ disease, certain groups face a higher risk of severe illness:
- Adults over 50
- Current or former smokers
- People with chronic lung diseases like COPD, emphysema, or asthma
- Individuals with weakened immune systems from illnesses or treatments (such as cancer, diabetes, kidney failure, or organ transplant medications)
These groups should be especially alert for symptoms if they live, work, or spend time near the affected neighborhoods in Harlem.
Treatment and Recovery
The good news is that Legionnaires’ disease is treatable with antibiotics if caught early. According to the CDC and NYC health officials, most people who receive timely treatment recover fully. However, untreated cases can progress quickly and become life-threatening.
Anyone in the affected areas who develops a cough, fever, or breathing difficulties should seek medical attention immediately and mention the outbreak to their healthcare provider. This helps doctors test for Legionella and start antibiotics without delay.
What NYC Is Doing Now
New York City’s Department of Health has launched a public awareness campaign in Central Harlem, urging residents to recognize symptoms and get tested if they feel sick. City crews are testing and cleaning cooling towers in the area to prevent further spread.
Acting Health Commissioner Dr. Michelle Morse emphasized that tap water in Harlem is safe. Residents can continue to drink it, cook with it, bathe, and use air conditioners in their homes without concern. The danger lies only in breathing in mist from contaminated large-scale cooling systems.
Lessons From Past Outbreaks
This is not the first time New York has dealt with Legionnaires’ disease. In 2015, a major outbreak in the Bronx infected more than 120 people and killed 12. That event led to new city regulations requiring regular inspection and cleaning of cooling towers.
Despite these rules, smaller outbreaks still occur, often linked to lapses in maintenance or unexpected bacterial growth. Experts stress that consistent monitoring is key to preventing future outbreaks.
What You Can Do to Protect Yourself
While individuals can’t control cooling tower maintenance, there are steps you can take to lower your risk:
- Be aware of outbreaks in your area and avoid lingering near mist from large air conditioning units or fountains during active cases.
- Get medical care quickly if you develop flu-like symptoms and live or work in an affected neighborhood.
- If you manage a building with a cooling tower, follow NYC Health Department requirements for testing and cleaning.
- Support regular public health inspections to ensure buildings meet safety standards.
Why Awareness Matters
Legionnaires’ disease remains underdiagnosed because its symptoms mimic other respiratory illnesses. Many cases are never confirmed because patients are treated for pneumonia without specific Legionella testing. Public awareness helps both residents and healthcare providers catch outbreaks earlier and prevent more severe outcomes.
The current Harlem outbreak is a reminder that environmental health risks can emerge quietly and spread before most people even know they exist. Vigilance, quick action, and strong public health systems are the best defenses against illnesses like this.
