An outbreak of Legionnaires' disease in the Harlem area of New York City has resulted in the deaths of two people and the diagnosis of at least 58 others, officials reported Monday. The New York City Health Department is urging residents and workers in the affected area to seek medical attention if they experience flu-like symptoms.

The Health Department initially reported one fatality and 22 confirmed cases last Thursday. The numbers have since climbed, prompting a heightened public health alert.

Legionnaires' disease is a serious type of pneumonia caused by the Legionella bacteria, which is found in fresh water sources and can contaminate man-made water systems like cooling towers and hot tubs.

The disease spreads when people inhale mist or small water droplets containing the bacteria, and symptoms, which typically appear 2-14 days after exposure, can include fever, cough, shortness of breath, and muscle aches. It is not transmitted from person to person and is treated with antibiotics, ABC News reported.