Table 1.
Characteristics of study population
| Variable | Screened only | Enrolled | Complete data |
| No. of participants | 177 | 178 | 142 |
| Breath collection visits | 0 | 278 | 218 |
| Male (%) | 89 (50) | 91 (51) | 69 (49) |
| Influenza vaccination current season (%) | 53 (30) | 42 (24) | 31 (22) |
| Influenza vaccination previous season (%) | 77 (44) | 63 (35) | 48 (34) |
| Influenza vaccination current & previous (%) | 39 (22) | 32 (18) | 22 (15) |
| Asthma, self-reported (%) | – | 38 (21) | 30 (21) |
| Smoker, current (%) | – | 30 (17) | 21 (15) |
| Antiviral medication last 24 h (%) | 2 | 11 (6) | 7 (5) |
| Age, y (IQR) | 20 (19–22) | 21 (19–22) | 20 (19–21) |
| BMI (IQR) | 23.6 (21.3–26.2) | 23.2 (21.0–25.7) | 22.7 (20.9–25.5) |
| Body temperature measured (IQR) | 36.9 (36.8–37.1) | 37.2 (36.9–37.7) | 37.2 (36.9–37.6) |
| Median coughs/30 min (IQR)* | – | 17 (6–39) | 18 (5–39) |
| Median sneezes/30 min (IQR) | – | 0 (0-0) | 0 (0–0) |
| Median upper respiratory symptoms (IQR)† | 7 (4–9) | 6 (5–8) | 7 (5–8) |
| Median lower respiratory symptoms (IQR) | 2 (1–4) | 3 (2–5) | 3 (2–6) |
| Median systemic symptoms (IQR) | 6 (3–9) | 8 (5–11) | 8 (5–11) |
IQR = interquartile range.
*
Cough, sneeze, and symptom scores are reported per visit.
†
Twelve symptoms were rated from 0 to 3 with maximum possible composite score of 15 for upper respiratory, 9 for lower respiratory, and 15 for systemic symptoms.