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Volume 32, Number 1—January 2026

Research

Effect of Chloramine Disinfection of Community Water System on Legionnaires’ Disease Outbreak, Minnesota, USA, 2024

Molly E. Bledsoe1, Apoorva Goel, Maya Adelgren, Timothy M. LaPara2, and Raymond M. Hozalski2Comments to Author 
Author affiliation: University of Minnesota–Twin Cities, Minneapolis, Minnesota, USA (M.E. Bledsoe, A. Goel, M. Adelgren, T.M. LaPara, R.M. Hozalski); Biotechnology Institute, University of Minnesota–Twin Cities, St. Paul, Minnesota, USA (T.M. LaPara, R.M. Hozalski)

Main Article

Table 1

Concentrations of Legionella pneumophila as determined by Legiolert assay in water samples collected in study of Legionella and chloramine disinfection within a community water system, Minnesota, USA*

Location Description Concentration, log10 MPN/L
2024 Feb 2024 May 2024 Sep 2024 Dec
Water utility
 Finished water
 <LOD
 <LOD
 <LOD
 <LOD
A
 Distribution system
 1
 <LOD
 <LOD
 <LOD
B Distribution system <LOD <LOD <LOD <LOD
Premise, cold 3.7 2.0 <LOD <LOD
Premise, hot
 3.7
 2.4
 1.6
 <LOD
C Distribution system <LOD <LOD <LOD <LOD
Premise, cold <LOD <LOD <LOD <LOD
Premise, hot
 <LOD
 <LOD
 <LOD
 <LOD
D
 Distribution system
 <LOD
 <LOD
 <LOD
 <LOD
E Distribution system ND <LOD <LOD <LOD
Premise, cold ND <LOD <LOD <LOD
Premise, hot
 ND
 4.0
 <LOD
 <LOD
F
 Distribution system
 <LOD
 <LOD
 <LOD
 <LOD
G Distribution system <LOD <LOD <LOD <LOD

*Samples were collected on different dates and from different locations. Samples were classified as being from the distribution system or from the premise plumbing (cold or hot). Chloramine disinfection was initiated in June 2024. LOD, limit of detection; MPN, most probable number; ND, not determined because no sample was collected.

Main Article

1Current affiliation: Black & Veatch, Bloomington, Minnesota, USA.

2These authors contributed equally to this manuscript.

Page created: December 18, 2025
Page updated: January 29, 2026
Page reviewed: January 29, 2026
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
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