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.

A Legionnaires' disease outbreak in Harlem is blamed for at least three deaths, and NYC officials are warning to watch out for the symptoms.

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