Key Findings: Outbreaks and Water Management Gaps

Key points

  • We reviewed CDC-led Legionnaires’ disease outbreak investigations from 2015–2019.
  • All of the deficiencies associated with outbreaks could have been prevented by comprehensive, properly implemented water management programs (WMPs).
Man in a hard hat assessing water pipes.

Water management programs prevent deficiencies

We analyzed reports from CDC-led investigations of LD outbreaks to find deficiencies associated with outbreaks. We examined each deficiency by several criteria, including type of WMP deficiency and type of environmental deficiency (process, equipment, or human error or from unmanaged external change).

All of the deficiencies associated with outbreaks could have been prevented by comprehensive, properly implemented WMPs.

  • The most common WMP deficiencies were that a building lacked a WMP (43%) or the WMP would have been adequate but was not followed (implementation deficiency, 40%). An example of an implementation deficiency would be not measuring water heater temperatures as called for in the WMP.
  • Most environmental deficiencies (82%) were associated with a missing process or a process that could not prevent growth or spread of Legionella (process failure). The others were caused by human error or equipment failure.
Image of two pie charts with accompanying text. Title for first pie chart: Most WMP deficiencies associated with outbreaks were due to missing or improperly implemented WMPs (43% had no WMP in place, 40% had a WMP implementation deficiency, and 17% had a content deficiency). Title for second pie chart header: Most environmental deficiencies were due to process failure (82% process failure, 15% human error, and 4% equipment failure). Note that percentages may not total 100 due to rounding.
Characteristics of deficiencies associated with LD outbreaks

Important role of environmental health practitioners

Information gathered by environmental health (EH) practitioners during LD outbreak investigations describes water system management practices and maintenance deficiencies.

We created a method that EH practitioners can use to collect this type of information to help address gaps and target water management priorities. EH practitioners, building managers, and other public health staff can share and use this information to identify common causes of LD outbreaks and improve the use and content of WMPs.

What you can do

Take steps to improve water management in buildings and prevent LD outbreaks.

  • Building managers can increase use of WMPs to identify areas or devices in a building where Legionella might grow or spread to people. We found that all deficiencies associated with LD outbreaks could have been prevented through effective use of WMPs.
  • EH staff can collect and share data on common environmental and WMP deficiencies. This type of information sharing can improve WMP implementation.