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Table 1 Attack rates of acute Q-fever among residents within circular distance rings around each potential source (A-G) expressed per 100,000 persons over week 16-32 (14 April-10 August 2008), with relative risks (RR) and 95% confidence intervals (95% CI)

From: The use of a geographic information system to identify a dairy goat farm as the most likely source of an urban Q-fever outbreak

Distance from source A B C D E F G
0-1 kilometre        
Attack rate1 0 0 413 178 0 0 0
RR2 (95% CI) 0 0 53 (24-114) 8 (1-61) 0 0 0
Q-fever cases 0 0 35 1 0 0 0
Population 92 136 8482 562 119 281 1444
0-2 kilometre        
Attack rate 376 352 203 46 0 13 76
RR (95% CI) 31 (16-59) 25 (13-49) 26 (12-54) 2 (1-5) 0 1 (0-5) 5 (2-13)
Q-fever cases 33 27 59 6 0 1 8
Population 8788 7671 29,098 13,022 9852 7632 10,582
0-3 kilometre        
Attack rate 241 228 137 28 19 69 102
RR (95% CI) 20 (11-36) 16 (9-30) 18 (8-36) 1 (1-3) 1 (0-2) 4 (2-8) 7 (4-13)
Q-fever cases 59 58 69 9 4 12 28
Population 24,461 25,487 50,349 32,709 20,521 17,506 27,329
0-4 kilometre        
Attack rate 124 133 101 26 60 147 98
RR (95% CI) 10 (6-19) 10 (5-17) 13 (6-27) 1 (1-2) 2 (1-4) 8 (5-13) 7 (4-12)
Q-fever cases 70 66 71 15 19 49 62
Population 56,585 49,570 70,151 58,002 31,425 33,270 63,547
0-5 kilometre        
Attack rate 92 88 86 53 94 100 79
RR (95% CI) 8 (4-14) 6 (3-11) 11 (5-23) 3 (2-4) 4 (3-6) 5 (3-9) 6 (3-10)
Q-fever cases 71 74 78 51 54 71 72
Population 77,558 84,374 90,779 96,402 57,329 70,680 91,123
>5-10 kilometre        
Attack rate 12 14 8 21 25 18 14
RR 1 1 1 1 1 1 1
Q-fever cases 13 13 8 39 40 21 17
Population 107,680 93,469 102,192 185,269 162,141 113,966 121,978
  1. 1 Attack rate: number of Q-fever cases per 100,000 population during the outbreak
  2. 2 RR = relative risk, attack rate divided by the attack rate of the reference category 5-10 km, with 95% confidence interval (CI)