Table 1.
Comparison of epidemiological and laboratory characteristics.
| Features of outbreaks | Outbreak A | Outbreak B | Outbreak C |
|---|---|---|---|
| Epidemiological features | |||
| Attack rate (%) | 326/2007 (16.24) | 27/656 (4.1) | 36/214 (16.8) |
| Symptomatic patients | 326 | 27 | 36 |
| Date of onset | Nov 21, 2012 | Nov 30, 2012 | Nov 30, 2012 |
| Scale(s) | Large | Medium | Medium |
| Type of setting | School | School | School |
| Clinical symptoms (%) | |||
| Diarrhea | 326/326 (100) | 23/27 (85.2) | 26/36 (72.2) |
| Nausea | 223/326 (68.4) | 24/27 (88.9) | 24/36 (66.7) |
| Abdominal pain | 205/326 (62.9) | 25/27 (92.6) | 17/36 (47.2) |
| Vomiting | 156/326 (47.9) | 14/27 (51.9) | 26/36 (72.2) |
| Fever | 190/326 (58.3) | 14/27 (51.9) | 17/36 (47.2) |
| Laboratory test | |||
| No. of examinations of patients | 99 | 10 | 22 |
| Positive samples | 46 | 2 | 12 |
| Genogroup I | — | — | — |
| Genogroup II | 46 | 2 | 12 |
| No. of examinations of food-handlers | 28 | 14 | 5 |
| Positive samples | 2 | 5 | 2 |
| Genogroup I | — | — | — |
| Genogroup II | 2 | 5 | 2 |
| Environmental samples | 13 | ||
| Causative foods (unheated foods) | 9 | ||
| Genogroup I | — | ||
| Genogroup II | 9 | ||
| Supplemental water | 3 | ||
| Genogroup I | — | ||
| Genogroup II | 3 | ||
| Groundwater | 1 | ||
| Genogroup I | — | ||
| Genogroup II | 1 | ||