title: Unusual Legionnaires' outbreak in cool, dry Western Canada: an investigation using genomic epidemiology.
abstract: An outbreak of Legionnaires' disease occurred in an inner city district in Calgary, Canada. This outbreak spanned a 3-week period in November-December 2012, and a total of eight cases were identified. Four of these cases were critically ill requiring intensive care admission but there was no associated mortality. All cases tested positive for Legionella pneumophila serogroup 1 (LP1) by urinary antigen testing. Five of the eight patients were culture positive for LP1 from respiratory specimens. These isolates were further identified as Knoxville monoclonal subtype and sequence subtype ST222. Whole-genome sequencing revealed that the isolates differed by no more than a single vertically acquired single nucleotide variant, supporting a single point-source outbreak. Hypothesis-based environmental investigation and sampling was conducted; however, a definitive source was not identified. Geomapping of case movements within the affected urban sector revealed a 1·0 km common area of potential exposure, which coincided with multiple active construction sites that used water spray to minimize transient dust. This community point-source Legionnaires' disease outbreak is unique due to its ST222 subtype and occurrence in a relatively dry and cold weather setting in Western Canada. This report suggests community outbreaks of Legionella should not be overlooked as a possibility during late autumn and winter months in the Northern Hemisphere.
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
authors.forename: N C
authors.initials: NC
authors.lastname: Knox
authors.affiliation: National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada.
authors.forename: K A
authors.initials: KA
authors.lastname: Weedmark
authors.affiliation: Alberta Health Services, Calgary, Alberta, Canada.|O'Brien Institute for Public Health, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.|Department of Medicine, Cumming School of Medicine, Calgary, Alberta, Canada.|Department of Microbiology, Immunology and Infectious Diseases, Cumming School of Medicine, Calgary, Alberta, Canada.|Department of Pathology and Laboratory Medicine, Cumming School of Medicine, Calgary, Alberta, Canada.|Calvin, Phoebe and Joan Snyder Institute for Chronic Diseases, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.|Calgary Laboratory Services, Calgary, Alberta, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Conly
authors.affiliation: Department of Biochemistry, Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada.|Public Health Ontario, Toronto, Ontario, Canada.
authors.forename: A W
authors.initials: AW
authors.lastname: Ensminger
authors.affiliation: Alberta Health Services, Calgary, Alberta, Canada.|Department of Community Health Sciences, Cumming School of Medicine, Calgary, Alberta, Canada.
authors.forename: F S
authors.initials: FS
authors.lastname: Hosein
authors.affiliation: Alberta Health Services, Calgary, Alberta, Canada.|Department of Microbiology, Immunology and Infectious Diseases, Cumming School of Medicine, Calgary, Alberta, Canada.|Calvin, Phoebe and Joan Snyder Institute for Chronic Diseases, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: S J
authors.initials: SJ
authors.lastname: Drews
mesh_terms: D000368:Aged; D000942:Antigens, Bacterial / Q000652:urine; D001431:Bacteriological Techniques; D002170:Canada / Q000453:epidemiology; D004196:Disease Outbreaks; D005260:Female; D023281:Genomics; D005838:Genotype; D006801:Humans; D016952:Legionella pneumophila / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D007877:Legionnaires' Disease / Q000453:epidemiology* / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D058889:Molecular Typing; D013183:Sputum / Q000382:microbiology; D011795:Surveys and Questionnaires; D014505:Urban Population
chemical_list: D000942:Antigens, Bacterial
keywords: 
                 Legionella pneumophila
              ; Genomic analysis; Legionnaires' disease; ST222; Western Canada; outbreak