Outbreaks of Legionnaires' Disease and Pontiac Fever 2006-2017

The global importance of Legionnaires' disease (LD) and Pontiac fever (PF) has grown in recent years. While sporadic cases of LD and PF do not always provide contextual information for evaluating causes and drivers of Legionella risks, analysis of outbreaks provides an opportunity to assess these factors.

A review was performed and provides a summary of LD and PF outbreaks between 2006 and 2017. Of the 136 outbreaks, 115 were LD outbreaks, 4 were PF outbreaks, and 17 were mixed outbreaks of LD and PF. Cooling towers were implicated or suspected in the a large portion of LD or PF outbreaks (30% total outbreaks, 50% confirmed outbreak-associated cases, and 60% outbreak-associated deaths) over this period of time, while building water systems and pools/spas were also important contributors. Potable water/building water system outbreaks seldom identify specific building water system or fixture deficiencies. The outbreak data summarized here provides information for prioritizing and targeting risk analysis and mitigation strategies.