The cluster of the potentially fatal pneumonia-like illness was initially detected on July 25 and has since been identified across several zip codes in Harlem.

The disease is spread by breathing in water vapor containing Legionella bacteria, which are known to grow in cooling towers, whirlpool spas, hot tubs, humidifiers, hot water tanks and condensers of large air-conditioning systems.

New York City officials said they are investigating a cluster of Legionnaires' disease that has caused one death and nearly two dozen illnesses.