A Legionnaires' disease outbreak has sickened 18 people in Manhattan. Officials have traced the source to a contaminated cooling tower in the Upper East Side.

New York City Comptroller Mark Levine confirmed the cluster stems from a cooling tower, not a building's plumbing system. Health officials are investigating cases in the Carnegie Hill and Yorkville neighborhoods.

"This is not an issue with any building's plumbing system," the NYC Health Department stated. "Residents can continue to drink tap water, bathe, shower, cook, and use your air conditioner at home."

All cooling towers in the area are being tested. The bacteria are spread by inhaling contaminated water vapor.

Symptoms can appear two to ten days after exposure. They include fever, cough, shortness of breath, muscle aches, headaches, nausea, chest pain, and confusion.