Variable | Novel H1N1 influenza A | Seasonal influenza A | p-value |
Patients n | 75 | 52 | |
Age yrs | 39.7±16.7 | 69.6±17.0 | <0.001 |
Males | 39 (52) | 25 (48) | 0.664 |
Length of stay days median (IQR) | 6.0 (7.0) | 6.5 (6.5) | 0.217 |
Previous antibiotic therapy | 9 (12) | 7 (14) | 0.797 |
Comorbidity | |||
Structural lung disease | 18 (24) | 24 (46) | 0.009 |
Chronic heart failure | 0 (0) | 9 (17) | 0.002 |
Neurological disorder | 3 (4) | 11 (21) | 0.002 |
Alcoholism | 1 (1) | 6 (12) | 0.016 |
Pregnancy | 4 (5) | 0 (0) | 0.144 |
Influenza seasonal vaccination | 11(16) | 25(54) | <0.001 |
Pneumonia as cause of hospital admission | 58 (77) | 50 (96) | 0.004 |
Length of symptoms days median (IQR) | 5.0 (5) | 5.0 (3) | 0.705 |
Clinical manifestations | |||
Pharyngitis | 23 (31) | 20 (39) | 0.389 |
Fever | 72 (96) | 39 (75) | 0.005 |
Cough | 67 (91) | 46 (89) | 0.706 |
Chills | 32 (43) | 20 (39) | 0.653 |
Dyspnoea | 48 (65) | 37 (71) | 0.458 |
Chest pain | 20 (27) | 22 (42) | 0.073 |
Mental confusion | 4 (5) | 8 (15) | 0.057 |
Gastrointestinal symptoms | 18 (24) | 8 (16) | 0.264 |
Clinical findings | |||
Temperature °C | 38.1±1 | 37.7±1.1 | 0.039 |
Respiratory rate breaths·min−1 | 29.2±8 | 28.2±8.0 | 0.486 |
Systolic pressure mmHg | 133.7±24 | 131.3±22.5 | 0.566 |
Diastolic pressure mmHg | 81.5±19 | 72.6±11.5 | 0.001 |
Heart rate breaths·min−1 | 106.2±22 | 96.5±17.6 | 0.009 |
Crackles | 53 (71) | 18 (36) | <0.001 |
Laboratory findings | |||
Leukocyte count·mm−3 | 9.689±6.179 | 13.512±7.147 | 0.002 |
Serum creatinine μmol·L−1 median (IQR) | 104.3 (39.8) | 113.2 (26.5) | <0.001 |
Pa,O2 mmHg | 77.0±23.9 | 59.5±12.3 | <0.001 |
Pa,O2/FI,O2 <200 | 18 (28) | 5 (11) | 0.042 |
Radiography | |||
Alveolar | 35 (47) | 49 (94) | <0.001 |
Interstitial | 21 (28) | 3 (4) | <0.001 |
Mixed | 19 (25) | 1 (2) | <0.001 |
Complications | |||
ICU admission | 22 (29) | 4 (8) | 0.003 |
Mechanical ventilation | |||
None | 57 (76) | 50 (96) | 0.003 |
Invasive | 14 (19) | 1 (2) | 0.005 |
Noninvasive | 4 (5) | 1 (2) | 0.648 |
Septic shock | 5 (7) | 2 (4) | 0.699 |
Data are presented as mean±sd or n (%), unless otherwise stated. IQR: interquartile range; Pa,O2: arterial partial pressure of oxygen; FI,O2: inspiratory oxygen fraction; ICU: intensive care unit. Pa,O2 was on room air.