Table 3.
Distribution of Outbreak Size for Measles in Canada Between 2002 and 2013 and Estimates of the Reproduction Number (R) According to the Proportion of Imported Cases and Outbreak Size
| Outbreak Size |
Number of Cases |
% of Imported Cases |
Effective R |
||||||
|---|---|---|---|---|---|---|---|---|---|
| 1 Case Total (NL)a | 2 Cases Total (NL)a | ≥3 Cases Total (NL)a | All Total (NL)a | Total (NL)a | Crude % (n/N) | Correcteda % (n/N) | From Correctedb % Imported | From Correctedb Outbreak Size | |
| 2002 | 7 (3) | 7 (3) | 7 (3) | 57% (4/7) | 70% (7/10) | 0.30 (0.07–0.78) | 0 (0–0.19) | ||
| 2003 | 8 (1) | 2 (1) | 10 (2) | 16 (5) | 50% (8/16) | 56% (10/18) | 0.44 (0.20–0.83) | 0.11 (0.02–0.34) | |
| 2004 | 5 (1) | 1 | 6 (1) | 8 (1) | 63% (5/8) | 67% (6/9) | 0.33 (0.08–0.86) | 0.22 (0.04–0.69) | |
| 2005 | 4 (2) | 1 | 5 (2) | 6 (2) | 50% (3/6) | 63% (5/8) | 0.37 (0.09–0.97) | 0.12 (0.01–0.55) | |
| 2006 | 3 | 3 (1) | 1 (1) | 7 (2) | 13 (6) | 38% (5/13) | 47% (7/15) | 0.53 (0.24–0.99) | 0.40 (0.16–0.81) |
| 2007 | 3 (1) | 2 (1) | 5 (2) | 102 (97) | 3% (3/102) | 5% (5/104) | 0.95 (0.78–1.0) | 0.93 (0.76–1.13) | |
| 2008 | 5 (1) | 2 | 1 (1) | 8 (2) | 62 (54) | 10% (6/62) | 13% (8/64) | 0.87 (0.67–1.0) | 0.84 (0.64–1.09) |
| 2009 | 2 | 2 | 4 | 14 | 29% (4/14) | 29% (4/14) | 0.71 (0.36–1.0) | 0.71 (0.36–1.25) | |
| 2010 | 11 (3) | 1 (1) | 3 (2) | 15 (6) | 99 (85) | 9% (9/99) | 14% (15/105) | 0.86 (0.69–1.0) | 0.80 (0.64–0.98) |
| 2011 | 25 (1) | 4 (3) | 5 (2) | 34 (6) | 752 (20) | 4% (28/752) | 4% (34/758) | 0.96 (0.89–1.0) | 0.95 (0.88–1.02) |
| 2012 | 7 (1) | 1 | 8 (1) | 9 (1) | 78% (7/9) | 80% (8/10) | 0.20 (0.03–0.62) | 0.10 (0.01–0.44) | |
| 2013 | 12 (5) | 2 | 7 (5) | 21 (10) | 83 (26) | 13% (11/83) | 23% (21/93) | 0.77 (0.61–0.97) | 0.67 (0.51–0.85) |
| Total | 92 (19) | 14 (5) | 24 (13) | 130 (37) | 1171 (300) | 8% (93/1171) | 11% (130/1208) | 0.89 (0.84–0.95) | 0.86 (0.81–0.92) |
a Total (NL): Total number of outbreaks (outbreaks not linked to an imported case).
b Corrected for outbreaks not linked with an imported case. We assumed that for each of these outbreaks, only the imported case was missed, and we added these missed cases to both the numerator and denominator.