Table 1. Attack rates among exposed and unexposed groups, and relative risks by food item consumed, by school level and day, Listeria monocytogenes outbreak, Italy, May 2016 (n =484).
| Food |
Exposed | Unexposed | RR |
95% CI | ||||
|---|---|---|---|---|---|---|---|---|
| Total | Cases | % AR | Total | Cases | % AR | |||
| Two days before peaking | ||||||||
| School A | ||||||||
| Pasta with tomato sauce | 357 | 128 | 35.85 | 76 | 22 | 28.95 | 1.24 | 0.85-1.81 |
| Halibut | 338 | 126 | 37.28 | 95 | 24 | 25.26 | 1.48 | 1.02-2.14 |
| Courgettes | 202 | 74 | 36.63 | 231 | 76 | 32.90 | 1.11 | 0.86-1.44 |
| Bread | 328 | 112 | 34.15 | 105 | 38 | 36.19 | 0.94 | 0.70-1.27 |
| Fresh fruit | 277 | 105 | 37.91 | 156 | 45 | 28.85 | 1.31 | 0.98-1.75 |
| Water | 409 | 143 | 34.96 | 24 | 7 | 29.17 | 1.20 | 0.63-2.27 |
| Nursery (pupils aged 3-6) | ||||||||
| Pasta with tomato sauce | 293 | 93 | 31.74 | 62 | 15 | 24.19 | 1.31 | 0.82-2.10 |
| Halibut | 270 | 87 | 32.22 | 85 | 21 | 24.71 | 1.30 | 0.87-1.96 |
| Courgettes | 165 | 55 | 33.33 | 190 | 53 | 27.89 | 1.19 | 0.92-1.67 |
| Bread | 259 | 77 | 29.73 | 96 | 31 | 32.29 | 0.92 | 0.65-1.30 |
| Fresh fruit | 216 | 74 | 34.26 | 139 | 34 | 24.46 | 1.40 | 0.99-1.98 |
| Water | 336 | 104 | 30.95 | 19 | 4 | 21.05 | 1.47 | 0.61-3.56 |
| Primary school (pupils aged 6-10) | ||||||||
| Pasta with tomato sauce | 64 | 35 | 54.69 | 14 | 7 | 50.0 | 1.09 | 0.62-1.93 |
| Halibut | 68 | 39 | 57.35 | 10 | 3 | 30.0 | 1.91 | 0.73-5.04 |
| Courgettes | 37 | 19 | 51.35 | 41 | 23 | 56.10 | 0.92 | 0.60-1.39 |
| Bread | 69 | 35 | 50.72 | 9 | 7 | 77.78 | 0.65 | 0.43-0.99 |
| Fresh fruit | 61 | 31 | 50.82 | 17 | 11 | 64.71 | 0.79 | 0.51-1.2 |
| Water | 73 | 39 | 53.42 | 5 | 3 | 60.00 | 0.89 | 0.42-1.88 |
| One day before peaking | ||||||||
| School A | ||||||||
| Vegetables soup | 272 | 119 | 43.75 | 72 | 24 | 33.33 | 1.31 | 0.92-1.87 |
| Beef ham | 290 | 132 | 45.52 | 54 | 11 | 20.37 | 2.23 | 1.30-3.84 |
| Roasted potatoes | 286 | 114 | 39.86 | 58 | 29 | 50.00 | 0.8 | 0.59-1.07 |
| Bread | 267 | 107 | 40.07 | 77 | 36 | 46.75 | 0.86 | 0.65-1.13 |
| Fresh fruit | 242 | 103 | 42.56 | 102 | 40 | 39.22 | 1.09 | 0.82-1.44 |
| Water | 333 | 139 | 41.74 | 11 | 4 | 36.36 | 1.15 | 0.52-2.53 |
| Nursery (pupils aged 3-6) | ||||||||
| Vegetables soup | 205 | 85 | 41.46 | 59 | 17 | 28.81 | 1.44 | 0.93-2.22 |
| Beef ham | 224 | 93 | 41.52 | 40 | 9 | 22.50 | 1.85 | 1.02-3.35 |
| Roasted potatoes | 224 | 84 | 37.50 | 40 | 18 | 45.00 | 0.83 | 0.57-1.22 |
| Bread | 194 | 70 | 36.08 | 70 | 32 | 45.71 | 0.79 | 0.58-1.08 |
| Fresh fruit | 176 | 69 | 39.20 | 88 | 33 | 37.50 | 1.05 | 0.75-1.45 |
| Water | 257 | 99 | 38.52 | 7 | 3 | 42.86 | 0.9 | 0.38-2.14 |
| Primary school (pupils aged 6-10) | ||||||||
| Vegetables soup | 67 | 34 | 50.75 | 13 | 7 | 53.85 | 0.94 | 0.54-1.64 |
| Beef ham | 66 | 39 | 59.09 | 14 | 2 | 14.29 | 4.14 | 1.13-15.16 |
| Roasted potatoes | 62 | 30 | 48.39 | 18 | 11 | 61.11 | 0.79 | 0.51-1.24 |
| Bread | 73 | 37 | 50.68 | 7 | 4 | 57.14 | 0.89 | 0.45-1.75 |
| Fresh fruit | 66 | 34 | 51.52 | 14 | 7 | 50.00 | 1.03 | 0.58-1.83 |
| Water | 76 | 40 | 52.63 | 4 | 1 | 25.00 | 2.11 | 0.38-11.65 |
AR: attack rate; CI: confidence interval; RR: relative risk.
Significant associations are shown in bold.