NYC Legionella Outbreak from Cooling Towers

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News headline of Legionella outbreak in New York City.

Update as of 8-5-2025: 58 New Yorkers are sick with Legionnaires’ Disease, and 2 are dead from a recent Legionella outbreak caused by cooling tower(s).

Areas of New York City at Risk

The New York City Department of Health has identified areas of risk around Central Harlem. The following zip codes are where people are suspected of contracting the disease:

  • 10027- Part of Harlem that contains the Columbia University Campus.
  • 10030- North Manhattan neighborhood of Harlem.
  • 10035- East Harlem in Manhattan.
  • 10037- In Harlem, on the border of the Bronx.
  • 10039- Densely populated portion of Harlem.

Cooling Tower Outbreaks

Why routine testing of Legionella in cooling towers is important.

The cooling tower(s) that are likely to cause the outbreak in this area are being investigated. It is reported that the cooling towers in these suspected areas have all been tested for Legionella, and the ones with high levels of Legionella bacteria are being remediated.

Get a WMP For Water Maintenance

According to the CDC, remediation of Legionella in cooling towers should involve disinfection with chemicals such as chlorine, flushing the system, and cleaning the system. From here, more frequent testing is necessary, as well as a chemical water treatment program to help control future outbreaks from occurring.

How is it Being Spread?

Cooling towers function by evaporating water droplets into the air. If the cooling tower does not have regular chemical water treatment, the pneumonia-type bacteria called Legionella can grow. This bacterium then becomes airborne and can be breathed in by nearby tenants, workers, pedestrians, etc.

Regular testing (with remediation if high levels of bacteria are found) should be performed to help prevent the bacteria from infecting nearby populations.

Legionnaires’ Disease Origins

The American Legion is a community of United States war veterans. It is headquartered in Indianapolis, Indiana. In 1976, they hosted a convention in Philadelphia, Pennsylvania, at the Bellevue-Stratford Hotel.

Legionnaires' Disease origins at the Bellevue Stratford Hotel.

Unknown to those who attended the convention or stayed at the hotel, the Legionella bacteria were growing in the cooling tower and spreading throughout the building’s HVAC system. Over 182 cases were linked to this outbreak, and 29 people had died. This event led to increased regulations regarding cooling towers and Legionella control in Philadelphia and the United States.

East Coast Legionella Services

Regular testing of cooling towers and plumbing systems for Legionella is important to control outbreaks like this. Testing should be done in conjunction with a chemical water treatment plan to introduce biocides to the water that help control Legionella from growing. If Legionella bacteria are detected in high amounts, it is necessary to remediate the system, so Legionella does not spread via drinking water or water droplets in the air.

Chardon Labs Legionella Services Information

Chardon Labs services several areas on the East Coast for Legionella, including Pennsylvania, New York City, New Jersey, Washington D.C., Maryland, and Delaware. To learn more or have a free survey done, contact Chardon Labs here.

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Matt Welsh

Matt Welsh is the Vice President and Water Consultant at Chardon Labs. He helps consult a wide range of customers utilizing various methods of water treatment, from chemical to chemical-free approaches, large and small applications, and across a wide range of geographical influences. With 20 years of water treatment experience, including a wide range of troubleshooting and service in potable water and non-potable HVAC and industrial applications, he is an expert in water treatment chemistry for cooling towers, boilers, and closed-loop systems.

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