Table 1.
Sociodemographic characteristics and symptoms of enrollees ≥ 5 years of age reported at enrollment, by Polymerase Chain Reaction (PCR)-confirmed Influenza status
| Overall | Developmental sample | Validation sample | ||||
|---|---|---|---|---|---|---|
| Characteristics | PCR-negative for influenza | PCR-confirmed influenza | P valuea | |||
| Total | n = 3531 | n = 642 | Total | Total | ||
| N = 4173 | (84.6 %) | (15.4 %) | (N = 2087) | (N = 2086) | ||
| N (%) | n (%) | n (%) | N (%) | N (%) | ||
| Vaccinated by self-report | 354 (8.7) | 311 (87.8) | 43 (12.2) | 0.08 | 173 (8.5) | 181 (8.9) |
| Unvaccinated | 3714 (91.3) | 3131 (84.3) | 583 (15.7) | |||
| Smokerb | 436 (15.6) | 386 (88.5) | 50 (11.5) | 0.07 | 215 (15.2) | 221 (16) |
| Non-smoker | 2358 (84.4) | 2010 (85.2) | 348 (14.8) | |||
| Smoker in the household | 481 (11.6) | 428 (89.0) | 53 (11.0) | 0.004 | 223 (10.7) | 258 (12.4) |
| No smoker in the household | 3667 (88.4) | 3081 (84.0) | 586 (16.0) | |||
| Asthma diagnosis | 1098 (26.8) | 949 (86.4) | 149 (13.6) | 0.04 | 543 (26.4) | 555 (27.1) |
| No asthma diagnosis | 3007 (73.3) | 2521 (83.8) | 486 (16.2) | |||
| Any high risk condition | 1147 (85.0) | 1004 (87.5) | 143 (12.5) | 0.14 | 569 (84.4) | 578 (85.5) |
| No high risk condition | 203 (15.0) | 170 (83.7) | 33 (16.3) | |||
| Symptoms reported at enrollment | ||||||
| Fever | 2910 (69.7) | 2327 (80.0) | 583 (20.0) | <.001 | 1461 (70) | 1449 (69.5) |
| No fever | 1263 (30.3) | 1204 (95.3) | 59 (4.7) | |||
| Cough | 3818 (91.5) | 3189 (83.5) | 629 (16.5) | <.001 | 1912 (91.6) | 1906 (91.4) |
| No cough | 355 (8.5) | 342 (96.3) | 13 (3.7) | |||
| Fatigue | 3610 (86.5) | 3003 (83.2) | 607 (16.8) | <.001 | 1795 (86) | 1815 (87) |
| No fatigue | 563 (13.5) | 528 (93.8) | 35 (6.2) | |||
| Wheezing | 1550 (37.1) | 1292 (83.3) | 258 (16.7) | 0.08 | 773 (37) | 777 (37.2) |
| No wheezing | 2623 (62.9) | 2239 (85.4) | 384 (14.6) | |||
| Sore throat | 3105 (74.4) | 2639 (85.0) | 466 (15.0) | 0.25 | 1543 (73.9) | 1562 (74.9) |
| No sore throat | 1068 (25.6) | 892 (83.5) | 176 (16.5) | |||
| Nasal Congestion | 3351 (80.3) | 2823 (84.2) | 528 (15.8) | 0.18 | 1690 (81) | 1661 (79.6) |
| No nasal congestion | 821 (19.7) | 707 (86.1) | 114 (13.9) | |||
| Shortness of breath | 1899 (45.5) | 1598 (84.2) | 301 (15.8) | 0.45 | 911 (43.7) | 988 (47.4) |
| No shortness of breath | 2272 (54.5) | 1931 (85.0) | 341 (15.0) | |||
| Age, years, Mean (SD) | 34.1 (22.2) | 34.5 (22.2) | 31.9 (21.8) | 0.007 | 34.8 (22.3) | 33.5 (22) |
aFor difference between influenza cases and controls
bAsked of those ≥18 years only