Table 1 Evolution of the study groups in the follow-up study (adapted from reference 12)
From: A controlled survey of less typical long-term consequences after an extensive waterborne epidemic
Contaminated group | Control group | |
|---|---|---|
Population 2007 | 9 538 | 27 259 |
Original sample size | 1 021a | 1 000 |
Responded to the first study N (%) | 808 (79%) | 598 (60%) |
Sample size in the follow-up study (i.e., those who gave permission to be contacted again) | 615 | 343 |
Responded to the follow-up study N (%) % of the original sample | 323 (53%) 32% | 186 (54%) 19% |
Having had epidemic-related gastroenteritis during the epidemic, according to the follow-up study | 174 (54%) | 6 (3%) |