A 2015 outbreak of Legionnaires' disease, traced to a cooling tower at a hotel, forced New York City to address a problem that had long been suspected but never adequately addressed: the role of buildings in spreading Legionella bacteria through the air.

A Legionnaires' disease cluster in the Harlem area of New York City has caused five deaths and sickened over 100 people. Here's what it is, symptoms and how it's spread.

New York City officials have discovered a sixth death linked to a Legionnaires’ disease outbreak in Central Harlem, where more than 100 people have been diagnosed with the ailment.