Health Department Closes Investigation Of Harlem Legionnaires’ Disease Community Cluster

September 22, 2021

The Health Department today announced that the investigation of the Central Harlem Legionnaires’ disease community cluster is over. No new cases of Legionnaires’ disease have been identified in the area for four weeks and the cooling towers in the affected areas have completed disinfection as directed by the Health Department. There were 18 cases of Legionnaires’ disease associated with this cluster. All 18 people were hospitalized and 16 have been discharged. There have been no deaths.

The Health Department’s Public Health Laboratory analyzed sputum samples from patients and water samples from the cooling towers in the investigation area. The Lab’s analyses showed that the bacteria from one of the clinical specimens matched a cooling tower at NYC Health + Hospitals/Harlem.

“I’m grateful for the many Health Department staff who identified and responded to this cluster quickly,” said Health Commissioner Dr. Dave A. Chokshi. “After an extensive investigation, we were able to identify one cooling tower that matched to a clinical specimen, and appropriate cleaning and disinfection measures at that tower and all other potential sources were conducted.”

All facilities with cooling towers in the cluster area fully cooperated with the Health Department and those with Legionella positive results completed full cleaning and disinfection as directed.


Legionnaires’ disease is a type of pneumonia that is caused by the bacteria Legionella, which grows in warm water. Symptoms resemble other types of pneumonia and can include fever, chills, muscle aches, and cough. Most cases of Legionnaires’ disease can be traced to contamination of artificial water systems where conditions are favorable for Legionella growth, such as cooling towers or evaporative condensers associated with air conditioning and industrial cooling, whirlpool spas, hot tubs, decorative fountains and water features, hot water tanks, and complex plumbing system systems.

Individuals only get sick by breathing in water vapor containing Legionella bacteria, and the disease is not transmitted from person to person. Legionnaires’ disease is not caused by drinking water that has Legionella bacteria. Individuals at higher risk include those ages 50 and above, cigarette smokers, and people with chronic lung disease or compromised immune systems.

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