{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T17:51:59Z","timestamp":1788976319407,"version":"build-2803163510"},"reference-count":51,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2022,3,3]],"date-time":"2022-03-03T00:00:00Z","timestamp":1646265600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100006454","name":"Federal Food Safety and Veterinary Office","doi-asserted-by":"publisher","award":["Aramis nr.:4.20.01"],"award-info":[{"award-number":["Aramis nr.:4.20.01"]}],"id":[{"id":"10.13039\/501100006454","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002329","name":"Federal Office of Public Health","doi-asserted-by":"publisher","award":["Aramis nr.:4.20.01"],"award-info":[{"award-number":["Aramis nr.:4.20.01"]}],"id":[{"id":"10.13039\/501100002329","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Federal Office of Energy, Switzerland","award":["Aramis nr.:4.20.01"],"award-info":[{"award-number":["Aramis nr.:4.20.01"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Microorganisms"],"abstract":"<jats:p>When stay-at-home orders were issued to slow the spread of COVID-19, building occupancy (and water demand) was drastically decreased in many buildings. There was concern that widespread low water demand may cause unprecedented Legionella occurrence and Legionnaires\u2019 disease incidence. In lieu of evidenced-based guidance, many people flushed their water systems as a preventative measure, using highly variable practices. Here, we present field-scale research from a building before, during, and after periods of low occupancy, and controlled stagnation experiments. We document no change, a &gt; 4-log increase, and a &gt; 1.5-log decrease of L. pneumophila during 3- to 7-week periods of low water demand. L. pneumophila increased by &gt; 1-log after precautionary flushing prior to reoccupancy, which was repeated in controlled boiler flushing experiments. These results demonstrate that the impact of low water demand (colloquially called stagnation) is not as straight forward as is generally assumed, and that some flushing practices have potential unintended consequences. In particular, stagnation must be considered in context with other Legionella growth factors like temperature and flow profiles. Boiler flushing practices that dramatically increase the flow rate and rapidly deplete boiler temperature may mobilize Legionella present in biofilms and sediment.<\/jats:p>","DOI":"10.3390\/microorganisms10030555","type":"journal-article","created":{"date-parts":[[2022,3,3]],"date-time":"2022-03-03T09:24:53Z","timestamp":1646299493000},"page":"555","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":38,"title":["Variable Legionella Response to Building Occupancy Patterns and Precautionary Flushing"],"prefix":"10.3390","volume":"10","author":[{"given":"William J.","family":"Rhoads","sequence":"first","affiliation":[{"name":"Department of Environmental Microbiology, Eawag\u2014Swiss Federal Institute of Aquatic Science and Technology, 8306 Deubendorf, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Meril","family":"Sindelar","sequence":"additional","affiliation":[{"name":"Department of Environmental Microbiology, Eawag\u2014Swiss Federal Institute of Aquatic Science and Technology, 8306 Deubendorf, Switzerland"},{"name":"Department of Biology, ETH Zurich, 8092 Zurich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"C\u00e9line","family":"Margot","sequence":"additional","affiliation":[{"name":"Department of Environmental Microbiology, Eawag\u2014Swiss Federal Institute of Aquatic Science and Technology, 8306 Deubendorf, Switzerland"},{"name":"Department of Environmental Systems Science, ETH Zurich, 8092 Zurich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nadine","family":"Graf","sequence":"additional","affiliation":[{"name":"Department of Environmental Microbiology, Eawag\u2014Swiss Federal Institute of Aquatic Science and Technology, 8306 Deubendorf, Switzerland"},{"name":"Department of Environmental Systems Science, ETH Zurich, 8092 Zurich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Frederik","family":"Hammes","sequence":"additional","affiliation":[{"name":"Department of Environmental Microbiology, Eawag\u2014Swiss Federal Institute of Aquatic Science and Technology, 8306 Deubendorf, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,3,3]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Ciesielski, C.A., Blaser, M.J., and Wang, W.L. 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