A Legionnaires' disease cluster in the Harlem area of New York City has caused three deaths and over 80 people to be sickened. Here's what it is, symptoms and how it's spread.

New York City officials gathered Thursday to address the growing concern regarding the cluster of Legionnaires’ disease cases in Central Harlem. As of Thursday afternoon, three people had died of the disease.

Here’s what to know about Legionnaires’ disease, how it spreads, and the East Harlem cooling tower outbreak under investigation.