Table 2 Characteristics of laboratory-confirmed A/H1N1 influenza inpatients according to admission delay, Mexico, 01 April through 31 December, 2009

Days from symptoms onset to admission

Group 1 < =2 days

Group 2 > 2 days

No. of patients (% of all study inpatients)

2223 (58%)

1610 (42%)

P < 0.0001

Disease outcome

Deaths, No. (%)

177(8%)

375 (23.3%)

P < 0.0001

Pandemic wave

Spring wave

73 (50.3%)

72 (49.7%)

P = 0.085

Summer wave

223 (61.1%)

142 (38.9%)

Fall wave

1927 (58.0%)

1396 (42.0%)

Gender

Females, No. (%)

1293 (58.2%)

889 (55.2%)

P = 0.07

Age group (y), No. (% in each group)

< 18

800 (65.4%)

424 (34.6%)

P < 0.0001

18–49

1114 (56.5%)

857 (43.5%)

>50

307 (48.3%)

328 (51.7%)

Spring wave

31 (44.3%)

39 (55.7%)

P = 0.003

Summer wave

114 (64.4%)

63 (35.6%)

Fall wave

197 (65.7%)

103 (34.3%)