Table 3. Seasonal occurrence of verotoxigenic E. coli (VTEC), L. monocytogenes, Salmonella, or any of the three in the Sumas and/or Serpentine watersheds.
| Winter | Spring | Summer | Fall | |
|---|---|---|---|---|
| Sumas Watershed | ||||
| VTEC | 2/25 (8%) | 2/39 (5.1%) | 0/45 (0%) | 1/20 (5%) |
| L. monocytogenes | 2/25 (8%) | 1/39 (2.6%) | 2/45 (4.4%) | 1/20 (5%) |
| Salmonella | 2/25 (8%) | 1/39 (2.6%) | 1/45 (2.2%) | 1/20 (5%) |
| Any | 5/25 (20%) | 4/39 (10.3%) | 3/45 (6.7%) | 2/20 (10%) |
| Serpentine Watershed | ||||
| VTEC | 1/18 (5.6%) | 3/25 (12%) | 1/36 (2.8%) | 1/15 (6.7%) |
| L. monocytogenesα | 5/18 (27.8%) | 4/25 (16%) | 1/36 (2.8%) | 7/15 (46.7%) |
| Salmonella | 0/18 (0%) | 0/25 (0%) | 0/36 (0%) | 1/15 (6.7%) |
| Anyα | 5/18 (27.8%) | 6/25 (24%) | 2/36 (5.6%) | 8/15 (53.3%) |
| Both Watersheds | ||||
| VTEC | 3/43 (7%) | 5/64 (7.8%) | 1/81 (1.2%) | 2/35 (5.7%) |
| L. monocytogenesα | 7/43 (16.3%) | 5/64 (7.8%) | 3/81 (3.7%) | 8/35 (22.9%) |
| Salmonella | 2/43 (4.7%) | 1/64 (1.6%) | 1/81 (1.2%) | 2/35 (5.7%) |
| Anyα | 10/43 (23.3%) | 10/64 (15.6%) | 5/81 (6.2%) | 10/35 (28.6%) |
Winter = Dec-Feb; Spring = Mar-May; Summer = Jun-Aug; Fall = Sep-Nov
α Significant seasonal variation was observed for this pathogen(s) within respective watershed(s) (Fisher exact test; p < 0.05).