A Shelter-associated Tuberculosis Outbreak: A Novel Strain Introduced Through Foreign-born Populations

Abstract

I n low TB incidence countries such as Canada, TB disease remains concentrated in urban settings with outbreaks involving homeless and under-housed populations that continue to challenge TB control programs. While the incidence of TB in Canada declined to 4.7/100,000 in 2009, the burden of TB cases continues to be diagnosed among foreign-born (FB) individuals. 1 In Alberta, the rate of TB among the FB is 17.7/100,000, compared to the Canadian-born (CB) population at 1.7/100,000. 1 Other descriptions of homeless and under-housed populations in Canadian urban centres have reported that disease remains concentrated among CB-Aboriginal (CB-AB) populations, 2 though the rise in the proportion of FB cases among homeless populations has been noted. 3 Although cases of TB in the FB represent the majority of cases in Alberta, there had previously been little documented transmission to other FB or to CB individuals. 4 The objective of this study is to describe the transmission of TB from FB populations to CB populations through shelterbased locations in the inner city of Edmonton, Alberta. METHODS Study population Edmonton is a northern Canadian city with a population of 1,024,820; 18.5% of the population are immigrants. 5 The homeless population is estimated to be 3,079 and is concentrated in the inner city of Edmonton. 6 All cases of TB in the province are centrally reported to TB Services. Between May 2008 and December 2009, 103 cases of active TB were reported within Edmonton (mean annual rate for 2008 and 2009 was 7.9/100,000); 19 cases were linked to three locations (one apartment building and three homeless shelters) within a one-block area of the inner city. Demographic and clinical characteristics A retrospective review of these 19 cases was completed by extracting demographic, clinical, treatment and contact tracing data from iPHIS. All TB cases were culture-confirmed at the Provincial Laboratory for Public Health (Edmonton, Alberta). Contacts were identified through social networking interviews and through resident lists of shared communal-living locations. Contact investigation was limited to chest x-ray (CXR), sputum for acid-fast bacilli (AFB) analysis and symptom inquiry.

Investigation of a cluster of multi-drug resistant tuberculosis in a high-rise apartment block in Singapore

“…The likelihood of infecting others with TB is dependent on multiple factors such as the characteristics of cases and those exposed, the implicated bacterium and the environment (Escombe et al, 2007). TB outbreaks have also been associated with smear positivity and prolonged infectiousness (Moreau et al, 2012). The index case had high bacillary load (4+) on sputum smear, was symptomatic for four months prior to diagnosis, defaulted treatment after five days and was only located six weeks later (Chee et al, 2015).…”

“…These cities are also at an increased risk of imported strains, including drug-resistant TB, arising from rural to urban migration (Wang et al, 2011). Although uncommon, outbreaks of TB in modern apartment buildings have occasionally been reported (Dawson et al, 2016;Moreau et al, 2012). However, there have not been reports of phylogenetically-linked MDR-TB cases within high-rise apartments.…”

Éclosion de tuberculose chez les consommateurs de drogues et les sans-abri du Grand Montréal, Canada, de 2003 à 2016

“…Nous avons également localisé une zone périphérique en Montérégie, liée à un cas particulièrement contagieux, possiblement associé à un nouveau profil de consommation de substances que l'on retrouve principalement en milieu résidentiel (18). Les refuges ou les centres de réadaptation en dépendance ont aussi été visités par plusieurs cas au fil du temps, comme à Edmonton, où la transmission était manifestement associée à un petit nombre de refuges (8).…”

“…Comme dans la plupart des pays où l'incidence est faible, la tuberculose est concentrée dans des groupes précisprincipalement au sein de populations autochtones et chez les migrants en provenance de pays où la maladie est endémique. Toutefois, des éclosions ont été déclarées à Vancouver, à Toronto, à Edmonton et à Ottawa ainsi que dans plusieurs villes des États-Unis, généralement au sein de groupes présentant des facteurs de risque, tels qu'une co-infection VIH (sida), l'itinérance, la consommation abusive d'alcool ou de drogues et l'incarcération (2)(3)(4)(5)(6)(7)(8)(9)(10)(11). Bien que les données sur les taux d'incidence de tuberculose active au sein de ces groupes sont rares, un taux d'incidence de 13,2/100 000 personnes-années a été rapporté chez les sans-abri à Montréal (7).…”

“…Direction régionale de santé publique du Centre intégré universitaire de santé et de services sociaux du Centre-Sud-de-l'Île-de-Montréal, Montréal (Québec) 2 Programme canadien d'épidémiologie de terrain, Agence de la santé publique du Canada, Ottawa (Ontario) 3 Direction de santé publique du Centre intégré de santé et de services sociaux de la Montérégie-Centre, Longueuil (Québec) 4 Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke (Québec) 5 Direction de santé publique du Centre intégré de santé et de services sociaux de Laval, Laval (Québec) 6 Direction de la protection de la santé publique, Ministère de la Santé et des Services sociaux du Québec, Montréal (Québec) 7 Département d'épidémiologie, biostatistique et santé au travail, Université McGill, Montréal (Québec) 8 Laboratoire de santé publique du Québec, Sainte-Anne-de-Bellevue (Québec)…”