European Swine Influenza Network Report on Swine Influenza A Viruses Evolution and Diversity in Europe from October 2022 to September 2023

The European Swine Influenza Network (ESFLU) has been established as a COST Action scientific network and its primary objective is to foster scientific collaboration and enhance capacity at the European level for monitoring the evolution and spread of swine influenza A viruses (swIAVs), as well as identifying measures to prevent the spread of swIAVs within and between European countries. This report is the result of collaborative efforts with ESFLU Working Group 2 members sharing swIAV sequences derived from samples collected and sequenced between October 2022 and September 2023, the initial period of the ESFLU COST Action. To achieve this, rigorous phylogenetic analyses were conducted on the compiled sequences of about 250 swIAV strains. These analyses sought to determine the diversity of swIAVs in specific countries and their respective proportions based on the classification and analysis of HA sequences, with additional analyses on their NA sequences. Moreover, the analyses aimed to ascertain whether certain viruses had potentially traversed national boundaries, indicating the cross-border movement of these viruses.