The number of people with Legionnaires’ disease grew by nearly four times from 2000–2014, according to a new report by the US CDC. Legionnaires’ disease is deadly for about 10% of people who get it, the CDC said, and emphasized that 90% of outbreaks were caused by problems that are preventable with more effective water management.

In the last year, about 5,000 people were diagnosed with Legionnaires’ disease and more than 20 outbreaks were reported to CDC, according to the report.

“Many of the Legionnaire’s disease outbreaks in the United States over the past 15 years could have been prevented,” said CDC Director Tom Frieden, MD, MPH. “Better water system management is the best way to reduce illness and save lives, and today’s report promotes tools to make that happen.”

The Vital Signs report examined 27 building-associated Legionnaires’ disease outbreaks investigated by CDC across 24 states and territories, Mexico, and Canada. Sources of building-associated Legionnaires’ disease outbreaks were:

  • Drinkable water (56%), such as water used for showering;
  • Cooling towers (22%)
  • Hot tubs (7%)
  • Industrial equipment (4%)
  • Decorative fountain/water feature (4%).
  • Source not identified (0.7%).

Twenty-three of the investigations included descriptions of failures that contributed to the outbreak. In nearly half, more than one type of failure was identified.

  • 65% were due to process failures, like not having a Legionella water management program.
  • 52% were due to human error, such as a hot tub filter not being cleaned or replaced as recommended by the manufacturer.
  • 35% were due to equipment, such as a disinfection system, not working.
  • 35% were due to changes in water quality from reasons external to the building itself, like nearby construction.

In response, the CDC released a new toolkit for building owners and managers that provides a checklist to help identify if a water management program is needed, examples to help identify where Legionella could grow and spread in a building, and ways to reduce the risk of Legionella contamination.