A systematic, prospective, passive monitoring of circulating subtypes of influenza A virus in Danish pigs wascarried out in 2021. The overall purpose of the monitoring was to identify which influenza virus subtypesand genotypes that circulated among Danish pigs.In 2021, a total of 2895 influenza A virus tests were performed on 857 submissions from 647 herdsregistered with different CHR no. In total, 453 (53 %) of the submissions from 377 different herds had atleast one positive sample. Submissions were distributed across the country. There were a higher number ofsubmissions during the winter, but influenza positive samples were detected all year round, with atendency to a higher positive proportion from September-December.Virus with an HA gene of pandemic H1N1pdm09 origin (H1pdm09) was detected in 189 submissions from164 herds registered with different CHR no. and thereby accounted for 42 % of the influenza A viruspositive submissions. The proportion of H1pdm09 is thereby significantly higher than last year where only29 % of the positive submission had an HA gene of H1N1pdm09 origin. In total, 312 influenza A viruspositive submissions were subtyped for both HA and NA. These analyzes showed that the most commonOvervågning af influenza A i svin, december 2022Side 7 af 31subtypes in Danish pigs in 2021 were H1avN2sw, H1pdm09N1av and H1N1pdm09. Similarly to last year, theprevalence of the H1pdm09N1av subtype increased and this subtype now represents 24 % of allsubmissions for which both HA and NA were subtyped. At the same time, the H1avN2sw subtype hasdecreased in prevalence, and was constituting only 54 % of all subtyped submissions. For the first time inDenmark, two human zoonotic infections with H1N1pdm09 and H1pdm09N1av viruses originating fromDanish swine, were documented. This emphasizes that viruses with a zoonotic potential are present in theDanish swine population. In addition, low cross-reaction to the human seasonal flu is expected as thegenetic and antigenic drift of the H1pdm09Nx viruses in swine is significant.