Table 5.
Influenza severity and complications by RT-PCR result
| Category | Influenza-negative | Influenza-positive | P-value influenza-negative vs. positive | A(H1N1)pdm09 | A(H3N2) | B/Yamagata lineage | P-value for distribution by strain | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| N = 7437 | N = 2177 | N = 115 | N = 1231 | N = 646 | ||||||||
| n | % | n | % | n | % | n | % | n | % | |||
| Severity indicator | ||||||||||||
| Intensive care unit admission | 184 | 2.5 | 31 | 1.4 | 0.0020 | 4 | 3.5 | 15 | 1.2 | 9 | 1.4 | 0.2400 |
| Mechanical ventilation | 123 | 1.7 | 20 | 0.9 | <0.0001 | 1 | 0.9 | 14 | 1.1 | 4 | 0.6 | 0.5230 |
| Extracorporeal membrane oxygenation | 184 | 2.8 | 25 | 1.3 | 0.0020 | 3 | 2.6 | 9 | 0.8 | 9 | 1.7 | 0.1600 |
| Death during hospitalisation | 131 | 1.8 | 32 | 1.5 | 0.3460 | 1 | 0.9 | 26 | 2.1 | 3 | 0.5 | 0.0080 |
| Length of stay (days), median (interquartile range) | 6 | (4-9) | 6 | (4-8) | 0.0612 | 6 | (3-8) | 6 | (3-8) | 6 | (4-8) | 0.2835 |
| Pulmonary complications | <0.0001 | <0.0001 | ||||||||||
| None | 1939 | 26.1 | 1212 | 55.7 | 53 | 46.1 | 697 | 56.6 | 353 | 54.6 | ||
| Pneumonia | 1545 | 20.8 | 364 | 16.7 | 18 | 15.7 | 214 | 17.4 | 109 | 16.9 | ||
| COPD exacerbation | 265 | 3.6 | 87 | 4.0 | 3 | 2.6 | 66 | 5.4 | 15 | 2.3 | ||
| Respiratory failure | 55 | 0.7 | 32 | 1.5 | 0 | 0.0 | 23 | 1.9 | 5 | 0.8 | ||
| Asthma exacerbation | 28 | 0.4 | 12 | 0.6 | 0 | 0.0 | 11 | 0.9 | 1 | 0.2 | ||
| pulmonary collapse | 5 | 0.1 | 1 | 0.0 | 0 | 0.0 | 1 | 0.1 | 0 | 0.0 | ||
| Acute respiratory distress syndrome | 7 | 0.1 | 2 | 0.1 | 0 | 0.0 | 2 | 0.2 | 0 | 0.0 | ||
| Bronchiolitis | 416 | 5.6 | 201 | 9.2 | 15 | 13.0 | 91 | 7.4 | 75 | 11.6 | ||
| Upper respiratory infection | 3172 | 42.7 | 266 | 12.2 | 26 | 22.6 | 126 | 10.2 | 88 | 13.6 | ||
| Metabolic failure | 0.4690 | 0.3530 | ||||||||||
| Acute renal failure | 87 | 1.2 | 32 | 1.5 | 1 | 0.9 | 24 | 1.9 | 5 | 0.8 | ||
| Diabetic coma | 4 | 0.1 | 2 | 0.1 | 0 | 0.0 | 1 | 0.1 | 0 | 0.0 | ||
| Fluid/electrolyte/acid-base/balance disorders | 80 | 1.1 | 29 | 1.3 | 1 | 0.9 | 19 | 1.5 | 7 | 1.1 | ||
| Cardiovascular events | 0.3390 | <0.0001 | ||||||||||
| None | 6335 | 85.2 | 1883 | 86.5 | 107 | 93.0 | 991 | 80.5 | 612 | 94.7 | ||
| Acute myocardial infarction | 8 | 0.1 | 5 | 0.2 | 0 | 0.0 | 5 | 0.4 | 0 | 0.0 | ||
| Acute heart failure | 1 | 0.0 | 1 | 0.0 | 0 | 0.0 | 1 | 0.1 | 0 | 0.0 | ||
| Cardiac arrest | 4 | 0.1 | 3 | 0.1 | 0 | 0.0 | 3 | 0.2 | 0 | 0.0 | ||
| Malignant hypertension | 37 | 0.5 | 10 | 0.5 | 0 | 0.0 | 9 | 0.7 | 1 | 0.2 | ||
| Any cardiovascular condition | 1050 | 14.1 | 275 | 12.6 | 8 | 7.0 | 222 | 18.0 | 33 | 5.0 | ||
| Systemic inflammatory response syndrome, shock, or disseminated intravascular coagulation | 76 | 1.0 | 12 | 0.6 | 0.0320 | 2 | 1.7 | 9 | 0.7 | 1 | 0.2 | 0.0810 |
| Neurologic events | ||||||||||||
| No | 7423 | 99.8 | 2173 | 99.8 | 0.3140 | 114 | 99.1 | 1228 | 99.8 | 646 | 100.0 | 0.1249 |
| Altered mental status | 10 | 0.1 | 4 | 0.2 | 1 | 0.9 | 3 | 0.2 | 0 | 0.0 | ||
| Convulsions | 4 | 0.1 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | ||
| Major discharge diagnoses | <0.0001 | <0.0001 | ||||||||||
| Influenza | 124 | 1.7 | 1266 | 58.2 | 76 | 66.1 | 603 | 49.0 | 456 | 70.6 | ||
| Pneumonia | 1807 | 24.3 | 223 | 10.2 | 10 | 8.7 | 145 | 11.8 | 59 | 9.1 | ||
| Other respiratory disease | 3653 | 49.1 | 290 | 13.3 | 20 | 17.4 | 188 | 15.3 | 57 | 8.8 | ||
| Cardiovascular | 603 | 8.1 | 117 | 5.4 | 0 | 0.0 | 105 | 8.5 | 7 | 1.1 | ||
| Other | 1250 | 16.8 | 281 | 12.9 | 9 | 7.8 | 190 | 15.4 | 67 | 10.4 | ||