Disentangling the drivers and host-mediated global spread of H7 influenza A virus.

Avian influenza H7 viruses pose a significant zoonotic and pandemic threat, yet their evolutionary dynamics, spatial transmission patterns, and host-specific roles remain underexplored. This study integrates phylodynamic and phylogeographic analyses to map global H7 dissemination, quantify host-specific contributions, and identify key ecological and anthropogenic drivers. Epidemiological data show key epidemic waves in Asia during 2013-2014 and 2016-2017, and in Africa in 2023. The Eurasian and American lineages of H7 viruses exhibit transmission with a median velocity of ~661 km/year and ~354 km/year, though spread varies significantly by virus subtype. Anseriformes (~587 km/year) and wild birds (~654 km/year) spread the Eurasian lineage of H7 viruses more rapidly and over greater distances than Galliformes and domestic birds. Geographic distance is negatively associated with the spread of the H7 virus, while temperature and poultry density show positive association. In this work, we identify Asia as an important H7 virus evolutionary epicenter. Anseriformes drives transcontinental spread, whereas Galliformes facilitates local amplification. The dynamics of the H7 virus are shaped by ecological and socioeconomic factors. A One Health approach emphasizing targeted surveillance and global cooperation is essential to mitigate cross-species transmission and future pandemic threats.