Highly Pathogenic Avian Influenza Virus in Mammals: Lack of Detection in Cattle With Respiratory Tract Infections and Genetic Analysis of Sporadic Spillover Infections in Wild Mammals in Bavaria, Southern Germany, 2022–2023

Our results indicate a high frequency of spillover events to red foxes at a time when there was a peak of H5N1 infections in wild birds in Bavaria. Phylogenetic analyses show no specifically close genetic relationship between viruses detected in mammalian predators within a geographic area. While direct fox-to-fox transmission has not yet been reported, the H5N1 clade 2.3.4.4b AIVs' ability to spread through non-traditional interfaces and to cross species barriers underlines the importance of continuous IAV surveillance in mammals and possibly including previously unknown host species.