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Free Content Use of geographic and genotyping tools to characterise tuberculosis transmission in Montreal

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Abstract:

SETTING: In Canada, tuberculosis (TB) is increasingly an urban health problem. Montreal is Canada's second-largest city and the second most frequent destination for new immigrants and refugees.

OBJECTIVES: To detect spatial aggregation of cases, areas of excess incidence and local ‘hot spots’ of transmission in Montreal.

DESIGN: We used residential addresses to geocode active TB cases reported on the Island of Montreal in 1996–2000. After a hot spot analysis suggested two areas of overconcentration, we conducted a spatial scan, with census tracts (population 2500–8000) as the primary unit of analysis and stratification by birthplace. We linked these analyses with genotyping of all available Mycobacterium tuberculosis isolates, using IS6110-RFLP and spoligotyping.

RESULTS: We identified four areas of excess incidence among the foreign-born (incidence rate ratios 1.3–4.1, relative to the entire Island) and one such area among the Canadian-born (incidence rate ratio 2.3). There was partial overlap with the two hot spots. Genotyping indicated ongoing transmission among the foreign-born within the largest high-incidence zone. While this zone overlapped the area of high incidence among Canadian-born, genotyping largely excluded transmission between the two groups.

CONCLUSIONS: In a city with low overall incidence, spatial and molecular analyses highlighted ongoing local transmission.

Keywords: geographic information system; molecular epidemiology; tuberculosis

Document Type: Regular Paper

Affiliations: 1: Department of Geography, McGill University, Montreal, Quebec, Canada 2: Division of Medical Microbiology and Infectious Diseases, McGill University, Montreal, Quebec, Canada; and Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada 3: Respiratory Epidemiology Unit, McGill University, Montreal, Quebec, Canada; and Department of Epidemiology and Biostatistics, McGill University, Montreal, Quebec, Canada 4: Laboratoire de Santé Publique du Québec, Montreal, Quebec, Canada 5: Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada; and Division of Clinical Epidemiology, McGill University, Montreal, Quebec, Canada 6: Respiratory Epidemiology Unit, McGill University, Montreal, Quebec, Canada; and Respiratory Division, McGill University, Montreal, Quebec, Canada

Publication date: 2007-06-01

More about this publication?
  • The International Journal of Tuberculosis and Lung Disease publishes articles on all aspects of lung health, including public health-related issues such as training programmes, cost-benefit analysis, legislation, epidemiology, intervention studies and health systems research. The IJTLD is dedicated to the continuing education of physicians and health personnel and the dissemination of information on tuberculosis and lung health world-wide.

    Certain IJTLD articles are selected for translation into French, Spanish, Chinese or Russian. They are available on the Union website

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