Did you know that the world’s largest outbreak of Legionnaires’ disease occurred in July 2001 in Murcia, Spain? More than 800 cases were suspected, with 449 confirmed cases and six fatalities. To blame? The cooling towers at a city hospital, according to an epidemiologic investigation.

The Centers for Disease Control and Prevention (CDC) has stated that Legionnaires’ disease cases in the United States have risen by a staggering 286 percent since 2000, and a recent test of 196 cooling towers across the U.S. revealed that 84 percent were positive for the Legionella bacteria.

Despite the fact that cooling towers are a known source for transmitting the bacteria, legislators and activists can’t agree on what steps to take to prevent outbreaks. After a 2016 Legionnaires’ outbreak in Hopkins, MN, that sickened 23 and produced one death, State Rep. Cheryl Youakim (DFL-Hopkins) introduced a bill to create a state registry of cooling towers to more quickly identify the source of outbreaks.

Meanwhile, the nonprofit Alliance to Prevent Legionnaires’ Disease – which is supported by cooling-tower manufacturers – believes drinking water, not cooling towers, should be the primary concern of Legionnaires’ prevention. “The focus … on building equipment is misplaced,” Daryn Cline, who works for the Alliance and cooling-tower manufacturer Evapco, said in an interview with the Minneapolis Star Tribune. “More must be done to better monitor and disinfect against Legionella in the public drinking-water system.”

The only thing known for certain is there is still much to learn about Legionnaires’ disease. It has been 16 years since the Murcia event, and deaths and illnesses are still occurring due to Legionella infection from cooling towers.