Table 1

Characteristics of the cases with influenza and matched controls from the general population of Sweden in the age range 20–65 years in a national case–control study covering 1 July 2006 to 31 December 2019

Influenza (N=14 971)Controls (N=66 216)
Men44.1% (N=6595)43.8% (N=29 001)
Born in Sweden73.7% (N=11 035)83.2% (N=55 114)
Post high school examination39.7% (N=5947)43.9% (N=5947)
Chronic obstructive pulmonary disease*1.7% (N=250)0.1% (N=82)
Diabetes mellitus*5.5% (N=828)1.6% (N=1040)
Ischaemic heart disease*2.2% (N=794)0.7% (N=458)
Dispensed corticosteroids16.3% (N=2442)3.9% (N=2594)
Occupational exposures or dimensions of transmission and mitigation factors
No; workers (>30) in close proximity to each other30.6% (N=4582)26.8% (N=17 722)
Nature of contacts; regular contacts with infected patients21.5% (N=3220)16.3% (N=10 804)
Contaminated workspaces; frequently sharing material/surfaces with general public46.2% (N=6924)39.9% (N=26 401)
Location; working mostly inside73.7% (N=11 041)69.7% (N=46 174)
Social distancing; Can never be maintained30.2% (N=4524)24.3% (N=16 103)
Physical proximity; work very close (near touching) to other persons†30.6% (N=4573)24.2% (N=16 015)
Daily exposure to diseases or infections9.9% (N=1481)7.6% (n=1 481)
  • *Hospital-based diagnoses.

  • †Military personnel not included.