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) | |
| Men | 44.1% (N=6595) | 43.8% (N=29 001) |
| Born in Sweden | 73.7% (N=11 035) | 83.2% (N=55 114) |
| Post high school examination | 39.7% (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 corticosteroids | 16.3% (N=2442) | 3.9% (N=2594) |
| Occupational exposures or dimensions of transmission and mitigation factors | ||
| No; workers (>30) in close proximity to each other | 30.6% (N=4582) | 26.8% (N=17 722) |
| Nature of contacts; regular contacts with infected patients | 21.5% (N=3220) | 16.3% (N=10 804) |
| Contaminated workspaces; frequently sharing material/surfaces with general public | 46.2% (N=6924) | 39.9% (N=26 401) |
| Location; working mostly inside | 73.7% (N=11 041) | 69.7% (N=46 174) |
| Social distancing; Can never be maintained | 30.2% (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 infections | 9.9% (N=1481) | 7.6% (n=1 481) |
*Hospital-based diagnoses.
†Military personnel not included.