Quantifying the risk of high pathogenicity avian influenza virus spillover from wild birds to poultry farms in Denmark

A spatiotemporal mechanistic model was developed to assess the spillover risk of high pathogenicity avian influenza (HPAI) from wild birds to poultry farms in Denmark, with a focus on the 2020/2021 epidemic season. The model firstly estimates environmental contamination over time, from five wild bird species selected for their ability to spread HPAI. Secondly, the model quantifies the risk of transmission to poultry farms from the environment. For six domestic flock types (chicken, duck, turkey, mallard, other single-gamebird, and mixed species) transmission parameters regarding susceptibility were derived from literature, and dose-response relationships were used to quantify the potential of spillover into poultry farms. Cluster analysis identified consistent high-risk areas in South Zealand throughout the year, corresponding to a hot spot identified in the reported outbreak data. A good model precision (78%) was found, whereas the specificity ranged from 50% to 77%, depending on the time of the year.