Scientists say low chlorine levels in Flint’s water system during the city’s water crisis in 2014 and 2015 led the bacterium Legionella pneumophila to proliferate, causing a deadly outbreak of Legionnaire’s disease.

Scientists say low chlorine levels in Flint’s water system during the city’s water crisis in 2014 and 2015 led the bacterium Legionella pneumophila to proliferate, causing a deadly outbreak of Legionnaire’s disease.