Use of geographic and genotyping tools to characterise tuberculosis transmission in Montreal.
METHODS
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.


OBJECTIVE
To detect spatial aggregation of cases, areas of excess incidence and local 'hot spots' of transmission in Montreal.


METHODS
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.
Haase
I
I
Department of Geography, McGill University, Montreal, Quebec, Canada.
Olson
S
S
Behr
M A
MA
Wanyeki
I
I
Thibert
L
L
Scott
A
A
Zwerling
A
A
Ross
N
N
Brassard
P
P
Menzies
D
D
Schwartzman
K
K
D000328:Adult; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000032:analysis*; D004641:Emigration and Immigration / Q000706:statistics & numerical data; D005260:Female; D005838:Genotype; D006801:Humans; D015994:Incidence; D008297:Male; D008403:Mass Screening / Q000706:statistics & numerical data; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000302:isolation & purification; D012150:Polymorphism, Restriction Fragment Length; D011792:Quebec / Q000453:epidemiology; D012111:Residence Characteristics / Q000706:statistics & numerical data; D012189:Retrospective Studies; D014376:Tuberculosis / Q000453:epidemiology / Q000235:genetics / Q000382:microbiology / Q000635:transmission*; D014504:Urban Health / Q000706:statistics & numerical data
D004269:DNA, Bacterial