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.

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 who claim they contracted Legionnaires' disease while working at or near Harlem Hospital Center are suing contractors they allege failed to safeguard water cooling towers at the building against contamination by the bacteria that causes the illness.

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