<p>Supplementary Table 1: Strong one-sided reactivity (reciprocal geometric mean HI titre ≥ 40) against European porcine and human influenza viruses in healthy subjects with and without direct exposition to pigs</p><p> reciprocal HI≥40 against reciprocal HI<40 against European porcine influenza viruses European porcine influenza viruses no exposition to exposition to no exposition to exposition to titre against human influenza pigs pigs titre against human influenza pigs pigs viruses gender gender viruses gender gender percentage percentage percentage percentage median age median age median age median age profession profession H1N1 1m 4m 21m/12f 56m/13f 25.0% 20.0% 12.9% 20.2% A(H1N1)pdm09 A(H1N1)pdm09 47.0 y 46.5 y 40.0 y 43.0y reciprocal HI<40 reciprocal HI≥40 3 PF, 1 other 43 PF, 12 PV, 11 other, 3 n.i. 3m/1f 12m/3f 8m/10f 20m/7f 100.0% 75.0% 7.0% 7.9% seasonal H1N1 seasonal H1N1 39.5 y 35.0 y 33.5 y 46.0 y reciprocal HI<40 reciprocal HI≥40 8 PF, 7 other 12 PF, 10 PV, 1 S, 3 other, 1 n.i. H3N2 4m/2f 5m/6f 16m/8f 33m/10f 20.0% 16.2% 10.4% 14.6% A/Port Chalmers/1/1973 (H3N2) A/Port Chalmers/1/1973 (H3N2) 37.0y 31.0y 46.5 y 47.0 y reciprocal HI<40 reciprocal HI≥40 2 PF, 2 PV, 29 PF, 6 PV, 7 other 6 other, 2 n.i. 10m/6f 31m/14f 22m/30f 37m/10f 53.3% 66.2% 22.6% 16.0% seasonal H3N2 seasonal H3N2 38.5 y 39.0 y 35.0 y 46.0 y reciprocal HI<40 reciprocal HI≥40 26 PF, 6 PV, 1 S, 30 PF, 6 PV, 11 other, 1 n.i. 8 other, 3 n.i. Only samples with discriminative reciprocal HI titres against viral antigens of similar subtypes (irrespective of the different genetic origins) were considered in this table. The percentage refers to the absolute number of samples exhibiting a reciprocal HI≥40 or <40 with respect to exposition status. Used abbreviations: m: male; f: female; y: years; PF: pig farmer; PV: veterinarian taking care for pigs; S: slaughterer/butcher; n.i.: not indicated in detail</p>