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Analysis of risk factors of the two norovirus outbreaks.
| Contaminated drinking water | Exposed group | Unexposed group | RR | 95% CI | ||
|---|---|---|---|---|---|---|
| Cases | Total | Cases | Total | |||
| Outbreak A | 123 | 561 | 0 | 188 | 41.85 | 5.89–297.39 |
| Outbreak B | 88 | 326 | 0 | 290 | 79.23 | 11.11–565.12 |
RR, risk ratio; RR was calculated by adding one in each exposure group; CI, confidential interval.
