A modelling exploration of potential spatiotemporal risk of high pathogenicity avian influenza virus introduction to Danish dairy herds through the contaminated environment

Circulation of high pathogenicity avian influenza virus (HPAIV) among cattle in the US as a result from spillover events from wild birds has been reported since 2024. The consequences have reduced animal welfare and milk production and increased human exposure to infections. With HPAIV detected in British sheep in March 2025 and bovine antibodies detected in Dutch dairy cow in January 2026, the threat of a wider spread in European ruminants has been underscored. To timely detect and react against the spread of HPAIV in cattle appearing in new regions, it is essential to assess the spatiotemporal risk from wild birds. We here utilised a previously developed spatiotemporal simulation model for avian influenza in birds in Denmark to assess the weekly risk of introduction to dairy herds in 10 by 10 km squares. We estimated that the peak risk period for potential transmission to dairy herds is between January and March. Areas with the highest risk estimates include northern Jutland and southern Zealand, associated with a dense dairy population and the wild bird migration corridor, respectively. While these results likely represent a worst-case scenario, as many Danish herds are housed indoors during the peak risk months, the model provides a crucial benchmark for environmental infection pressure. The results can be used as a guideline for where and when to monitor for HPAIV introductions to dairy herds in Denmark.