Abstract
Objective: An outbreak of tuberculosis (TB) in a large urban apartment building and three homeless shelters within a one-block radius in Edmonton, Alberta occurred between 2008 and 2009. The purpose of this report is to describe the transmission dynamics of this multiethnic, multicentre inner-city TB outbreak.
Methods: A retrospective chart review was conducted through the Integrated Public Health Information Systems (iPHIS) to extract demographic, clinical and treatment data as well as data for contacts for all 19 cases involved in the outbreak. TB isolates were genotyped using molecular IS6110 restriction fragment-length polymorphism (RFLP). Categorical variables were compared using Fisher’s exact test and continuous variables were analyzed using the Kruskal Wallis test.
Results: Two groups were identified through genotyping. One group consisted of 9 cases with a newly identified TB genotype circulating in Alberta. All of the cases in this group were among males and two thirds were among individuals from northeast Africa, with subsequent transmission into Canadian-born populations through exposure during shelter stays. The second group (n=3) identified were infected by a previously circulating strain of TB in Alberta and consisted of Canadian-born Aboriginal people.
Conclusion: This study demonstrates the transmission of a novel TB strain from foreign-born populations to Canadian-born populations through location-based settings serving vulnerable populations. This study highlights the changing demographic and emerging health concerns for under-housed populations in Canada.
Key words: Homeless persons, Mycobacterium tuberculosis, Canada, foreign-born, shelter, outbreak
Résumé
Objectif: Une éclosion de tuberculose s’est produite entre 2008 et 2009 dans un grand immeuble d’appartements et trois maisons d’hébergement pour sans-abri situés dans le même pâté de maisons à Edmonton, en Alberta. Nous décrivons la dynamique de transmission de cette éclosion multiethnique et multicentrique de tuberculose dans un quartier déshérité du centre-ville.
Méthode: Nous avons mené un examen rétrospectif des dossiers médicaux par le biais du Système intégré d’information sur la santé publique (SIISP) pour en extraire les données démographiques, cliniques et de traitement, ainsi que les noms des contacts des 19 cas impliqués dans l’éclosion. Les isolats de la tuberculose ont été génotypés à l’aide du polymorphisme de restriction (RFLP) de la séquence d’insertion IS6110. Les variables catégorielles ont été comparées selon la méthode exacte de Fisher, et les variables continues ont été analysées à l’aide du test de Kruskal-Wallis.
Résultats: Le génotypage a permis d’identifier deux groupes. Le premier comprenait 9 cas présentant un génotype de la tuberculose nouvellement identifié circulant en Alberta. Tous les cas de ce groupe étaient des hommes, et les deux tiers étaient d’origine nord-africaine; la transmission de la maladie dans la population née au Canada s’est faite lors de séjours dans des maisons d’hébergement pour sans-abri. Les membres du second groupe identifié (n=3), des Autochtones nés au Canada, avaient été infectés par une souche de la tuberculose ayant déjà circulé en Alberta.
Conclusion: Cette étude montre la transmission d’une nouvelle souche de la tuberculose d’une population née à l’étranger dans une population née au Canada, ceci dans un milieu au service de populations vulnérables. L’étude fait ressortir les changements démographiques dans la population des personnes mal logées au Canada et soulève de nouvelles préoccupations relatives à leur santé.
Mots clés: personnes sans domicile fixe, Mycobacterium tuberculosis, Canada, personnes nées à l’étranger, maisons d’hébergement, flambées épidémiques
Footnotes
Conflict of Interest: None to declare.
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