Table 4 Univariate analysis of risk factors for 30-day mortality

Demographic data

   Age (years) (median, IQR)

66.5, 57.7-75.5

54, 43-62

0.09

   Male sex

15 (68.2)

5 (55.6)

0.68

Underlying conditions

   Immunosuppression

4 (18.2)

1 (11.1)

1

   COPD

9 (40.9)

5 (55.6)

0.69

   Charlson score

6, 2-8

5, 3.5-6.5

0.65

   Influenza vaccination

5 (22.7)

2 (22.2)

1

Type of ICU

   Medical

13 (59.1)

8 (88.9)

0.20

   Surgical

9 (40.9)

1 (11.1)

Reason for admission to the ICU

   Severe respiratory failure

7 (31.8)

7 (77.8)

0.08

   Surgery

9 (40.9)

1 (11.1)

   Cardiac arrest

4 (18.2)

0

   Other

2 (9.1)

1 (11.1)

   APACHE II score

14.5, 11-16.2

16, 13-19.5

0.22

Characteristics of influenza

   Days of symptoms before diagnosis^a

3.5, 0-9

3, 1.5-5

0.87

   Days of ICU stay before diagnosis^a

   Unsuspected diagnosis

1, 0-14.5

1, 0-3

0.26

   Hospital acquired

12 (54.5)

3 (33.3)

0.43

   Fever

12 (54.5)

1 (11.1)

0.04

   Cough

15 (68.2)

7 (77.8)

0.68

   Dyspnea

14 (63.6)

9 (100)

0.07

   Localized infiltrate on chest radiograph

15 (68.2)

9 (100)

0.07

   Viral load at diagnosis

4 (18.2)

3 (33.3)

0.64

   Pneumonia

1.5, 0.3-2.4

1.8, 0.8-5.5

0.40

   Co-infection

15 (68.2)

8 (88.9)

0.38

6 (27.3)

2 (22.2)

1