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Table 5 Influenza severity and complications by RT-PCR result

From: Influenza epidemiology and influenza vaccine effectiveness during the 2014–2015 season: annual report from the Global Influenza Hospital Surveillance Network

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