A deadly Legionnaires' disease outbreak in New York City has set health and community leaders on a campaign to educate the public on ways to prevent the bacteria from growing and spreading.

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.