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Table 5 Cases distribution (and person-days at risk) for different levels of shower contaminations and associations' measure.

From: Pontiac fever: an operational definition for epidemiological studies

Contamination threshold Exposure categories Number of subjects with Pontiac fever (person-days at risk) RR (and p*)
CFU ≥ 103 L-1 Exposed
Unexposed
10 (24855)
13 (42001)
1.30 (0.33)
CFU ≥ 104 L-1 Exposed
Unexposed
9 (20928)
14 (45928)
1.41 (0.27)
Cells-FISH ≥ 104 L-1 Exposed
Unexposed
23 (56245)
0 (10611)
UD** (0.02)
Cells-FISH ≥ 105 L-1 Exposed
Unexposed
19 (48265)
4 (18591)
1.83 (0.19)
Cells-FISH ≥ 106 L-1 Exposed
Unexposed
11 (20185)
12 (46671)
2.12 (0.05)
  1. *p value are from one-sided tests
  2. **UD: undefined, because of 0 cases among unexposed
  3. CFU: cells count by culture
  4. Cells-FISH: cells count by FISH method