Rainwater left untreated in cooling towers atop city-owned Harlem Hospital fueled the Big Apple’s deadliest Legionnaire’s disease outbreak in a decade, the Rev. Al Sharpton charged Tuesday.

Lawsuit filed after a deadly Legionnaires' outbreak in Harlem, alleging negligence by construction firms and NYC.

A Legionnaires’ disease outbreak in Harlem has claimed a fourth life, with nearly 100 confirmed cases and more than a dozen people still hospitalized. For the first time, city officials have identified 12 cooling towers that tested positive for Legionella bacteria — including four city-owned buildings such as Harlem Hospital.

Two construction workers are suing over workplace safety after being hospitalized with Legionnaires’ disease amid a deadly outbreak in central Harlem. Their illnesses came after working near a Harlem Hospital Center cooling tower that tested positive for the bacteria that causes the disease.

The Legionnaires' disease outbreak in Harlem has been traced to 12 cooling towers, including several at city-run buildings, officials said.

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.