“A local public health agency investigation into an increase in community-acquired legionellosis June-September 2013 in Milwaukee, Wisconsin: Lessons from the frontlines”

From June to September 2013, the City of Milwaukee Health Department (MHD) noted an increase in Legionellosis reporting in City residents. Fifty-four (54) confirmed cases of Legionnaires disease (Ld) representing a five-fold increase as compared to previous five years during a similar time frame were reported to the MHD resulting in an immediate epidemiological and environmental investigation by department staff.   All but one of the 54 adult cases (29-77) were hospitalized with Legionella pneumophila Serogroup I infection, with no reported deaths.  73% of cases were African-American, 65% had one or more risk factors associated with Ld.  89% had a history of smoking.  No common reservoir of exposure including institutional, commercial or residential was identified through epidemiological analysis.  MHD conducted an environmental field survey and sampling of several potential sources of L. pneumophila.  Several cooling towers tested positive for L. pneumophila with distinct strains identified. Yet, none of the strains matched any clinical specimens obtained from confirmed cases. Risk communication to the public via media occurred throughout the investigation.  Further, MHD consulted with local water treatment experts to enhance understanding of seasonal cooling tower operation in the metropolitan area given cooler seasonal temperature and high number of precipitation events.    Lessons from this investigation suggest that LPHAs need to improve awareness of environmental conditions conducive to Legionella bacterium colonization and dissemination, better understand potential sources of exposure related to community-acquired case reports, develop communication strategies that appropriately characterize risk to the public, and support partnerships with building owners and engineers and water treatment professionals that mitigate Legionellosis occurrence within a community.