Table 2. Characteristics of included patients according to RT-PCR result.
Influenza negative | Influenza positive | A(H3N2)a | A(H1N1)pa | B/Yamagataa | ||||||
---|---|---|---|---|---|---|---|---|---|---|
N = 4217 | N = 1086 | N = 534 | N = 362 | N = 130 | ||||||
Characteristic | n | % | n | % | n | % | n | % | n | % |
Age in years, mean (standard deviation) | 30.9 (31.7) | 34.9 (28.6) | 30 (27.0) | 45.8* (29.3) | 30.6 (25.6) | |||||
Age group | ||||||||||
0–5 months | 503 | 11.9 | 54 | 5 | 22 | 4.1 | 21 | 5.8 | 3 | 2.3 |
6–11 months | 279 | 6.6 | 36 | 3.3 | 20 | 3.7 | 11 | 3 | 1 | 0.8 |
1–4 years | 905 | 21.5 | 181 | 16.7 | 100 | 18.7 | 44 | 12.2 | 23 | 17.7 |
5–17 years | 291 | 6.9 | 102 | 9.4 | 57 | 10.7 | 14 | 3.9 | 24 | 18.5 |
18–49 years | 929 | 22.0 | 349 | 32.1 | 214 | 40.1 | 70 | 19.4 | 49 | 37.7 |
50–64 years | 337 | 8.0 | 132 | 12.2 | 29 | 5.4 | 87 | 24.1 | 11 | 8.5 |
65–74 years | 304 | 7.2 | 94 | 8.7 | 32 | 6.0 | 51 | 14.1 | 8 | 6.2 |
75–84 years | 426 | 10.1 | 106 | 9.8 | 47 | 8.8 | 47 | 13 | 9 | 6.9 |
≥85 y | 243 | 5.8 | 32 | 2.9 | 13 | 2.4 | 16 | 4.4 | 2 | 1.5 |
Female | 1829 | 43.4 | 547 | 50.4* | 284 | 53.2* | 165 | 45.7 | 72 | 55.4* |
Number of underlying comorbidities | ||||||||||
0 | 2789 | 66.1 | 656 | 60.4 | 345 | 64.6 | 165 | 45.7 | 94 | 72.3 |
1 | 732 | 17.4 | 260 | 23.9* | 122 | 22.8* | 109 | 30.2* | 24 | 18.5 |
≥2 | 696 | 16.5 | 170 | 15.7 | 67 | 12.5 | 87 | 24.1* | 12 | 9.2 |
Underlying chronic diseases | ||||||||||
Cardiovascular disease | 685 | 17.1 | 189 | 18.4 | 91 | 17.9 | 80 | 22.8* | 13 | 12.3 |
COPD | 607 | 15.2 | 139 | 13.6 | 44 | 8.7* | 79 | 22.5* | 13 | 12.3 |
Asthma | 194 | 4.8 | 76 | 7.4* | 35 | 6.9 | 31 | 8.8* | 10 | 9.4 |
Immunodeficiency/organ transplant | 38 | 0.9 | 16 | 1.6 | 13 | 2.6* | 3 | 0.9 | 0 | 0 |
Diabetes | 390 | 9.7 | 105 | 10.2 | 30 | 5.9* | 67 | 19.1* | 5 | 4.7 |
Chronic renal impairment | 167 | 4.2 | 57 | 5.6 | 24 | 4.7 | 28 | 8* | 4 | 3.8 |
Chronic rheumatologic disease | 12 | 0.5 | 11 | 1.7* | 6 | 1.4 | 1 | 1.8 | 4 | 3.8* |
Chronic neuromuscular disease | 94 | 2.3 | 19 | 1.9 | 14 | 2.8 | 3 | 0.9* | 2 | 1.9 |
Active neoplasm | 130 | 3.2 | 29 | 2.8 | 13 | 2.6 | 15 | 4.3 | 0 | 0 |
Chronic liver disease | 65 | 1.6 | 23 | 2.2 | 10 | 2.0 | 11 | 3.1 | 1 | 0.9 |
Autoimmune disease | 32 | 0.8 | 16 | 1.6* | 8 | 1.6 | 6 | 1.7 | 2 | 1.9 |
Pregnant status (women 15–45 years) | 181 | 44.7 | 156 | 70.3* | 100 | 71.9* | 18 | 51.4. | 33 | 86.8* |
Obeseb | 701 | 16.9 | 194 | 18.1 | 77 | 14.6 | 95 | 26.5* | 14 | 10.9 |
Outpatient visits in the last 3 monthsc | ||||||||||
0 | 1283 | 30.5 | 306 | 28.2 | 172 | 32.2 | 85 | 23.6 | 30 | 23.1 |
1 | 919 | 21.8 | 241 | 22.2 | 93 | 17.4 | 112 | 31.1 | 19 | 14.6 |
≥2 | 2011 | 47.7 | 538 | 49.6 | 269 | 50.4 | 163 | 45.3 | 81 | 62.3* |
Smoking habitsd | ||||||||||
Current smoker | 1009 | 23.9 | 274 | 25.3 | 124 | 23.2 | 100 | 27.7 | 31 | 24 |
Past smoker | 813 | 19.3 | 200 | 18.4 | 96 | 18.0 | 75 | 20.8 | 24 | 18.6 |
Never smoked | 2392 | 56.8 | 611 | 56.3 | 314 | 58.8 | 186 | 51.5 | 74 | 57.4 |
Functional index (Barthel)e | ||||||||||
Total or severe dependence | 106 | 11.1 | 14 | 6.4 | 4 | 4.9 | 10 | 8.8 | 0 | 0 |
Moderate-mild dependence | 294 | 30.9 | 63 | 28.6 | 29 | 35.4 | 21 | 18.4 | 11 | 64.7* |
No dependence | 552 | 58.0 | 143 | 65.0* | 49 | 59.8 | 83 | 72.8* | 6 | 35.3 |
Days from onset of symptoms to swabbing | ||||||||||
0–2 days | 1569 | 37.2 | 465 | 42.8 | 261 | 48.9 | 128 | 35.5 | 47 | 36.2 |
3–4 days | 1595 | 37.8 | 418 | 38.5 | 199 | 37.3 | 141 | 39.1 | 58 | 44.6 |
5–7 days | 1053 | 25.0 | 203 | 18.7* | 74 | 13.9* | 92 | 25.5 | 25 | 19.2 |
Influenza vaccination ≥14 d from ILI onset | 714 | 16.9 | 138 | 12.7* | 46 | 8.6* | 84 | 23.3* | 5 | 3.8* |
a Comparison group, negative influenza admissions
b Obesity was defined as a body mass index ≥30 for subjects ≥18 years of age and as a z-score of body mass index for age >2 standard deviations for subjects <18 years of age. Data were missing for 79 influenza-negative patients and 12 influenza-positive patients.
c Data were missing for 4 influenza-negative patients and 1 influenza-positive patient.
d Data were missing for 3 influenza negative patients and 1 influenza-positive patient.
e Assessed for admissions ≥65 years of age. Data were missing for 21 influenza-negative patients and 12 influenza-positive patients.
*P<0.05 vs. influenza negative