Legionella pneumophila occurrence in reduced-occupancy buildings in 11 cities during the COVID-19 pandemic

In spring 2020, reduced water demand was an unintended consequence of COVID-19 pandemic-related building closures. Concerns arose that contaminants associated with water stagnation, such as Legionella pneumophila , could become prevalent. To investigate this potential public health risk, samples from 26 reduced-occupancy buildings across 11 cities in the United States, Canada, and Switzerland were analyzed for L. pneumophila using liquid culture (Legiolert, n=258) and DNA-based methods (qPCR/ddPCR, n=138). L. pneumophila culture-positivity was largely associated with just five buildings, each of which had specific design or operational deficiencies commonly associated with L. pneumophila occurrence. Samples from free chlorine buildings had higher culture-positivity (37%) than chloramine buildings (1%), and 78% of culture-positive samples occurred when the residual was ≤0.1 mg/L Cl2. Although overall sample positivities using culture- and DNA-based methods were equivalent (34% vs. 35%), there was disagreement between the methods in 13% of paired samples. Few buildings reported any water management activities, and L. pneumophila concentrations in flushed samples were occasionally greater than in first-draw samples. This study provides insight into how building plumbing characteristics and management practices contribute to L. pneumophila occurrence during low water use periods and can inform targeted prevention and mitigation efforts. Synopsis Statement Legionella pneumophila occurrence was evaluated in reduced-occupancy buildings during the COVID-19 pandemic across multiple cities. ![Figure][1] ### Competing Interest Statement IDEXX Laboratories, Inc. provided 300 free Legiolert kits and additional kits at a 15% discount for this study. IDEXX Laboratories, Inc. did not contribute to the design, analysis, or writing of this manuscript. The interpretation of results and opinions presented in the manuscript are those of the authors and do not necessarily reflect those of IDEXX Laboratories, Inc. ### Funding Statement IDEXX Laboratories, Inc. provided 300 free Legiolert kits and additional kits at a 15% discount for this study. IDEXX Laboratories, Inc. did not contribute to the design, analysis, or writing of this manuscript. The interpretation of results and opinions presented in the manuscript are those of the authors and do not necessarily reflect those of IDEXX Laboratories, Inc. K.S.D. was supported by the National Science Foundation (NSF) Graduate Research Fellowship under Grant No. DGE-1256260, the University of Michigan Blue Sky Grant, and the University of Michigan Rackham Predoctoral Fellowship. H.D.G. was supported by the National Science Foundation (NSF) Graduate Research Fellowship under Grant No. DGE-1752814. S.M.J was supported by Arizona State University engineering startup funds. S.P was supported by a University of Pittsburgh Central Development Research award. W.J.R. was supported by EAWAG discretionary funding. C.R.P., A.J.W., and C.L. were supported by NSF Grants No. CBET-2039498 and CBET-2027049. C.R.P. was supported by the Purdue University Lilian Gilbreth Postdoctoral Fellowship. S.V. and L.H. were supported by NSF Grants No. CBET-2029850 and CBET-1749530. Water Research Foundation Project 4721 additionally supported the development of qPCR/ddPCR methods applied in this study. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced are available online at [https://github.com/kathdowd/L.pneumophila\_study\_2022][2] [https://github.com/kathdowd/L.pneumophila\_study\_2022][2] [1]: pending:yes [2]: https://github.com/kathdowd/L.pneumophila_study_2022