Fifty-eight people were sickened and 12 died from a Legionnaires' disease (LD) outbreak in Quincy, IL, in 2015. The initial outbreak investigation identified deficiencies at the Illinois Veteran's Home (IVHQ), but these did not account for four community-acquired cases that occurred concurrently with no IVHQ exposure. We broaden the investigation to evaluate seven lines of evidence and assess whether municipal drinking water supply deficiencies potentially contributed to a community-wide outbreak. Notably, 3−6 months prior to the outbreak, the primary disinfectant was changed and corrosion control was interrupted, causing a sustained decrease in disinfectant residuals throughout Quincy's distribution system. We hypothesize this created more favorable conditions for Legionella growth throughout the system and an increase in water lead levels. These municipal system deficiencies were not identified in prior investigations of the outbreak, but their impacts on public health outcomes are consistent with those of the 2014−2016 Flint Water Crisis. However, they occurred in Quincy without any legal violations in the municipal water system or public acknowledgment of community-wide health risks. This study supports the critical need for improved data collection during changes in municipal water treatment. Additional regulatory and communication requirements can better protect public health from both LD and lead.

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A lack of replicable test systems that realistically simulate hot water premise plumbing conditions at the laboratory-scale is an obstacle to identifying key factors that support growth of opportunistic pathogens (OPs) and opportunities to stem disease transmission. Here we developed the convectively-mixed pipe reactor (CMPR) as a simple reproducible system, consisting of off-the-shelf plumbing materials, that self-mixes through natural convective currents and enables testing of multiple, replicated, and realistic premise plumbing conditions in parallel. A 10-week validation study was conducted, comparing three pipe materials (PVC, PVC-copper, and PVC-iron; n = 18 each) to stagnant control pipes without convective mixing (n = 3 each). Replicate CMPRs were found to yield consistent water chemistry as a function of pipe material, with differences becoming less discernable by week 9. Temperature, an overarching factor known to control OP growth, was consistently maintained across all 54 CMPRs, with a coefficient of variation <2%. Dissolved oxygen (DO) remained lower in PVC-iron (1.96 ± 0.29 mg/L) than in PVC (5.71 ± 0.22 mg/L) or PVC-copper (5.90 ± 0.38 mg/L) CMPRs as expected due to corrosion. Further, DO in PVC-iron CMPRs was 33% of that observed in corresponding stagnant pipes (6.03 ± 0.33 mg/L), demonstrating the important role of internal convective mixing in stimulating corrosion and microbiological respiration. 16S rRNA gene amplicon sequencing indicated that both bulk water (P adonis = 0.001, R 2 = 0.222, P betadis = 0.785) and biofilm (P adonis = 0.001, R 2 = 0.119, P betadis = 0.827) microbial communities differed between CMPR versus stagnant pipes, consistent with creation of a distinct ecological niche. Overall, CMPRs can provide a more realistic simulation of certain aspects of premise plumbing than reactors commonly applied in prior research, at a fraction of the cost, space, and water demand of large pilot-scale rigs.

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