A Legionnaires' disease cluster in the Harlem area of New York City has caused three deaths and 90 people to be sickened. Here's what it is, symptoms and how it's spread.

Seven new cases of Legionnaires’ have been reported since Friday in the Legionnaires’ outbreak, which has so far sickened 90 people and killed three. There are currently 17 people hospitalized from Legionnaires’, a severe form of pneumonia, down from more than 20 last week, according to city data.