Assessment of response bias among returning participants who enrolled in 2002 or 2003
| 2004 | 2006 | 2008 | ||||
| Participants | Terminates* | Participants | Terminates* | Participants | Terminates* | |
| Total n | 3280 | 1035 | 2572 | 1743 | 2309 | 2006 |
| Age at outbreak (mean±SD) | 36.4±22.1 | 32.3±21.8† | 37.4±22.1† | 32.5±21.8† | 37.9±22.1 | 32.6±21.8 |
| Female gender: n (%) | 1889 (57.6) | 530 (51.2)† | 1501 (58.4) | 918 (52.7)† | 1379 (59.7) | 1040 (51.8)† |
| Gastroenteritis during outbreak: n (%) | 2169 (66.1) | 712 (68.8) | 1706 (66.3) | 1175 (67.4) | 1528 (66.2) | 1353 (67.4) |
| Anxiety/depression: n (%) | 295 (9.0) | 110 (10.6) | 224 (8.7) | 181 (10.4) | 211 (9.1) | 194 (9.7) |
| Acute symptoms: n (%) | ||||||
| Abdominal cramps | 1923 (58.6) | 628 (60.7) | 1509 (58.7) | 1042 (59.8) | 1354 (58.6) | 1197 (59.7) |
| Fever | 886 (27.0) | 316 (30.5) | 686 (26.7) | 516 (29.6)† | 612 (26.5) | 590 (29.4)† |
| Weight loss | 493 (15.0) | 181 (17.5) | 391 (15.2) | 283 (16.2) | 335 (14.5) | 339 (16.9)† |
| Blood in stools | 544 (16.6) | 193 (18.6) | 440 (17.1) | 297 (17.0) | 405 (17.5) | 332 (16.6) |
| Duration of diarrhoea | ||||||
| <2 days | 140 (4.3) | 34 (3.3) | 113 (4.4) | 61 (3.5) | 108 (4.7) | 66 (3.3) |
| 2–3 days | 494 (15.1) | 155 (15.0) | 395 (15.4) | 254 (14.6) | 351 (15.2) | 298 (14.9) |
| 4–5 days | 341 (10.4) | 123 (11.9) | 272 (10.6) | 192 (11.0) | 254 (11.0) | 210 (10.5) |
| 6–7 days | 330 (10.1) | 117 (11.3) | 249 (9.7) | 198 (11.4)† | 226 (9.8) | 221 (11.0)† |
| >7 days | 661 (20.2) | 212 (20.5) | 511 (19.9) | 362 (20.8) | 444 (19.2) | 429 (21.4)† |
| Peak stool frequency | ||||||
| 1–3/day | 318 (9.7) | 114 (11.0) | 235 (9.1) | 197 (11.3) | 207 (9.0) | 225 (11.2) |
| 4–6/day | 663 (20.2) | 193 (18.6) | 527 (20.5) | 329 (18.9)† | 468 (20.3) | 338 (16.8)† |
| 7–10/day | 400 (12.2) | 159 (15.4) | 312 (12.1) | 247 (14.1) | 285 (12.3) | 274 (13.7) |
| >10/day | 462 (14.1) | 144 (13.9) | 371 (14.4) | 235 (13.5)† | 336 (14.6) | 270 (13.5)† |