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Table 1 Characteristics of cases of pandemic influenza reported in the initiation period (week 18 to week 41, 2009) and acceleration period (week 42 to week 46, 2009)

From: The first wave of pandemic influenza (H1N1) 2009 in Germany: From initiation to acceleration

  Number of cases with information Initiation period (%)a Acceleration period (%)a
Total 53,968 23,789 (44.1) 30,179 (55.9)
Age groups 53,930 23,783 30,147
   Median [quartiles]   19 [16,26]# 15 [10,26]#
   0-4 years 2,076 516 (2.2) 1,560 (5.2)
   5-14 years 16,989 3,794 (16.0) 13,195 (43.8)
   15-24 years 20,295 12,854 (54.0) 7,441 (24.7)
   25-59 years 13,975 6,398 (26.9) 7,577 (25.1)
   ≥ 60 years 595 221 (0.9) 374 (1.2)
Origin of infection 53,757 23,714 30,043
   Autochthonous cases 37,573 9,235 (38.9) 28,338 (94.3)
Risk factors 39,748 17,579 22,169
   All cases   820 (4.7)* 1,539 (6.9)*
Autochthonous cases 27,486 411/6,868 (6.0)** 1,458/20,618 (7.1)**
Imported cases 12,140 405/10,644 (3.8)** 77/1,476 (5.2)**
   Risk factors    
Chronic diseases    
Respiratory disease 1,080 372 (2.1) 708 (3.2)
Cardio-vascular disease 264 107 (0.6) 157 (0.7)
Diabetes 173 63 (0.4) 110 (0.5)
Obesity§ 159 71 (0.4) 88 (0.4)
Immunosuppression 112 40 (0.2) 72 (0.3)
Other chronic diseases 458 127 (0.7) 331 (1.5)
Pregnancy 113 40 (0.2) 73 (0.3)
Age groups 39,748 17,533 22,043
0-4 years 1,474 17/367 (4.6) 53/1.107 (4.8)
5-14 years 12,351 101/2,831 (3.6) 571/9,520 (6.0)
15-24 years 15,107 314/9,510 (3.3) 291/5,597 (5.2)
25-59 years 10,368 350/4,711 (7.4) 560/5,657 (9.9)
≥ 60 years 429 38/157 (24.2) 63/272 (23.2)
Symptoms 53,968 23,789 30,179
   ILI   2,318 (9.7) 2,924 (9.7)
Diagnosis    
   Time interval between onset of symptoms and diagnosis 7.253 3 days [2, 5]# 2 days [1,4]#
Antiviral treatment initiated 35,160 15,941 19,219
   All cases   4,671 (29.3) 4.491 (24.7)
Cases with underlying chronic disease 2,092 319/743 (42.9) 598/1,278 (46.8)
Cases without risk factors 33,139 4,352/15,198 (28.6) 3,893/17,941 (21.7)
Pregnancy 88 6/34 (17.6) 13/54 (24.1)
   Time interval between symptom onset and start of therapy   2 days [1,3]# 1 day [1,2]#
Pneumonia 40,729 18,090 22,639
   All cases with pneumonia 275 93 (0.5) 182 (0.8)
Antiviral treatment initiated 219 33/77 (42.9) 56/142 (39.4)
   Cases with underlying chronic disease 76 19/764 (2.5) 57/1,410 (4.0)
   Cases without risk factors 176 66/16,303 (0.4) 110/20,192 (0.5)
   Pregnancy 99 1/37 (2.7) 1/62(1.6)
Hospitalisation 52,485 23,665 28,820
   All cases hospitalised 2,084 1,117 (4.7)* 967 (3.4)*
Age (years)   19 [16,26]# 15 [11,26]#
   Cases with risk factors 2,342 102/814 (12.5) 182/1,528 (11.9)
Age (years)   23 [16,41] # 17 [11, 39] #
   Cases without risk factors 37,187 618/16,711 (3.7)* 597/20.476 (2.9)*
Age (years)   19 [16,25]# 15 [10,25]#
  1. # Lower/upper quartile
  2. § Obesity requiring treatment or body mass index > 30
  3. a The percentages in brackets refer to the number of cases with available information regarding the variable. In each cell the number printed in bold is used as denominators in a cell. If another denominator is used, it is given in the table.
  4. * Comparison initiation versus acceleration period: p < 0.001
  5. ** Comparison initiation versus acceleration period: p < 0.01