Publication Date



Legionella, pneumonia, bacteria, fresh water, waterways, Legionnaire’s disease, environment


Preliminary research has suggested possible associations between natural waterways and Legionella infection, and we previously explored these associations in eastern Wisconsin using positive L. pneumophila serogroup 1 urine antigen tests (LUAT) as diagnostic. This case-control study was a secondary analysis of home address data from patients who underwent LUAT at a single eastern Wisconsin health system from 2013 to 2017. Only zip codes within the health system’s catchment area that registered ≥ 3 positive cases and ≥ 50 completed tests, as well as geographically adjacent zip codes with ≥ 2 positive cases and ≥ 50 tests, were included. A 1:3 ratio of cases to randomly selected controls was used. Home addresses were geocoded and mapped using ArcGIS software (Esri); nearest waterway and distance to home was identified. Distance to nearest waterway according to ArcGIS was verified/corrected using Google Maps incognito. Distances were analyzed using chi-squared and 2-sample t-tests. Overall, mean distance to nearest waterway did not differ between cases (2958 ± 2049 ft) and controls (2856 ± 2018 ft; P = 0.701). However, in a subset of nonurban zip codes, cases were closer to nearest waterway than controls (1165 ± 905 ft vs 2113 ± 1710 ft; P = 0.019). No association was found between cases and type of waterway. Further research is needed to investigate associations and differences between natural and built environmental water sources in relation to legionellosis.




April 19th, 2021


July 6th, 2021


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