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Table 1 Significant high rate giardiasis spatial clusters in southern Ontario, 1990–98

From: Investigation of clusters of giardiasis using GIS and a spatial scan statistic

Clustera

No. of Cases in cluster

Expected No. of cases

Annual cases per 100,000 person-yrs

Cluster RRb

No. of CSDsc

P-value

1

936

491

3.7

1.91

1

0.001

2

908

502

3.5

1.81

1

0.001

3

1160

759

3

1.53

124

0.001

4

1102

744

2.9

1.48

60

0.001

5

340

166

4

2.05

1

0.001

6

177

84

4.1

2.12

1

0.001

7

439

290

2.9

1.51

5

0.001

8

23

3

13.5

7

1

0.001

9

16

1

22.3

11.5

1

0.001

10

33

8

7.4

4.34

2

0.001

11

751

586

2.5

1.23

3

0.001

12

21

3

12.2

6.3

1

0.001

13

25

6

7.8

4

1

0.001

14

103

56

3.5

1.83

11

0.001

15

14

2

13.2

6.81

1

0.001

16

21

5

8.2

4.23

1

0.001

17

23

8

5.9

3.06

1

0.001

18

276

212

2.5

1.3

14

0.001

19

96

61

3.1

1.59

2

0.056

20

19

6.3

5.8

3

1

0.082

  1. a See Figure 3 for the spatial distribution of the geographically large clusters b Rate ratio c Census Sub-divisions