A record 9,933 cases of Legionellosis were reported in 2018 according to numbers from the Centers for Disease Control and Prevention.
The figure, including both Legionnaires' disease and the milder Pontiac fever, is an increase from the 6,100 cases reported in 2016 and reflects a more than eight-fold increase over the last two decades, according to an article on the Becker's Hospital review website.
Hospitals spent $434 million treating Legionnaires' disease in 2012 alone and more flushing water systems to remove bacteria.
Rising temperatures, longer summers and the increased popularity of environmentally-friendly buildings may be contributing to the rise in Legionnaires'.