Gonzalo G Alvarez1,2,3,4, Alice A Zwerling1,4, Carla Duncan5, Christopher Pease2,3, Deborah Van Dyk2, Marcel A Behr4,6, Robyn S Lee4,6, Sunita Mulpuru1,2,3, Smita Pakhale1,2,3, D William Cameron1,2,3, Shawn D Aaron1,2,3, Michael Patterson7, Jean Allen8, Kathryn Sullivan9, Anne Jolly1, Meenu K Sharma10,11, Frances B Jamieson5,12. 1. School of Epidemiology and Public Health, University of Ottawa, Ottawa, Ontario, Canada. 2. Ottawa Hospital Research Institute, Ottawa, Ontario, Canada. 3. Department of Medicine, The Ottawa Hospital, Ottawa, Ontario, Canada. 4. McGill International Tuberculosis Centre, McGill University Health Centre, Montreal, Quebec, Canada. 5. Public Health Ontario Laboratory, Public Health Ontario, Toronto, Ontario, Canada. 6. The Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada. 7. Department of Health, Government of Nunavut, Iqaluit, Nunavut, Canada. 8. Nunavut Tunngavik Inc, Iqaluit, Nunavut, Canada. 9. School of Medicine, University of Ottawa, Ottawa, Ontario, Canada. 10. National Microbiology Laboratory, Public Health Agency of Canada, Winnipeg, Manitoba, Canada. 11. Department of Medical Microbiology and Infectious Diseases, Max Rady College of Medicine, University of Manitoba, Winnipeg, Manitoba, Canada. 12. Department of Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
Abstract
BACKGROUND: In the last decade, tuberculosis (TB) incidence among Inuit in the Canadian Arctic has been rising. Our aim was to better understand the transmission dynamics of TB in this remote region of Canada using whole-genome sequencing. METHODS: Isolates from patients who had culture-positive pulmonary TB in Iqaluit, Nunavut, between 2009 and 2015 underwent whole-genome sequencing (WGS). The number of transmission events between cases within clusters was calculated using a threshold of a ≤3 single nucleotide polymorphism (SNP) difference between isolates and then combined with detailed epidemiological data using a reproducible novel algorithm. Social network analysis of epidemiological data was used to support the WGS data analysis. RESULTS: During the study period, 140 Mycobacterium tuberculosis isolates from 135 cases were sequenced. Four clusters were identified, all from Euro-American lineage. One cluster represented 62% of all cases that were sequenced over the entire study period. In this cluster, 2 large chains of transmission were associated with 3 superspreading events in a homeless shelter. One of the superspreading events was linked to a nonsanctioned gambling house that resulted in further transmission. Shelter to nonshelter transmission was also confirmed. An algorithm developed for the determination of transmission events demonstrated very good reproducibility (κ score .98, 95% confidence interval, .97-1.0). CONCLUSIONS: Our study suggests that socioeconomic factors, namely residing in a homeless shelter and spending time in a gambling house, combined with the superspreading event effect may have been significant factors explaining the rise in cases in this predominantly Inuit Arctic community.
BACKGROUND: In the last decade, tuberculosis (TB) incidence among Inuit in the Canadian Arctic has been rising. Our aim was to better understand the transmission dynamics of TB in this remote region of Canada using whole-genome sequencing. METHODS: Isolates from patients who had culture-positive pulmonary TB in Iqaluit, Nunavut, between 2009 and 2015 underwent whole-genome sequencing (WGS). The number of transmission events between cases within clusters was calculated using a threshold of a ≤3 single nucleotide polymorphism (SNP) difference between isolates and then combined with detailed epidemiological data using a reproducible novel algorithm. Social network analysis of epidemiological data was used to support the WGS data analysis. RESULTS: During the study period, 140 Mycobacterium tuberculosis isolates from 135 cases were sequenced. Four clusters were identified, all from Euro-American lineage. One cluster represented 62% of all cases that were sequenced over the entire study period. In this cluster, 2 large chains of transmission were associated with 3 superspreading events in a homeless shelter. One of the superspreading events was linked to a nonsanctioned gambling house that resulted in further transmission. Shelter to nonshelter transmission was also confirmed. An algorithm developed for the determination of transmission events demonstrated very good reproducibility (κ score .98, 95% confidence interval, .97-1.0). CONCLUSIONS: Our study suggests that socioeconomic factors, namely residing in a homeless shelter and spending time in a gambling house, combined with the superspreading event effect may have been significant factors explaining the rise in cases in this predominantly Inuit Arctic community.
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Authors: Timothy M Walker; Camilla L C Ip; Ruth H Harrell; Jason T Evans; Georgia Kapatai; Martin J Dedicoat; David W Eyre; Daniel J Wilson; Peter M Hawkey; Derrick W Crook; Julian Parkhill; David Harris; A Sarah Walker; Rory Bowden; Philip Monk; E Grace Smith; Tim E A Peto Journal: Lancet Infect Dis Date: 2012-11-15 Impact factor: 25.071
Authors: K Bjorn-Mortensen; B Soborg; A Koch; K Ladefoged; M Merker; T Lillebaek; A B Andersen; S Niemann; T A Kohl Journal: Sci Rep Date: 2016-09-12 Impact factor: 4.379