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.

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.

About one in 10 people who get sick from Legionnaires' disease die from the disease due to complications from illness, CDC said.