Viral metagenomics reveals heterogeneity in mammalian virus hosting, sharing, and spillover.

Carnivores show significantly higher propensities to carry human-associated viruses than other mammalian orders, while bats rank lower in this zoonotic risk metric.

• Why it matters: Spillover risk may depend on which mammalian taxa host and share viruses, but prior host-virus association tests are biased by uneven sampling effort.
• What they did: The study analyzed 4,685 metagenomic datasets spanning 296 mammalian species across 14 orders, then used network and phylogenetic comparative analyses to link virus richness and transmission centrality to life-history and anthropogenic factors.
• The result: Host longevity and urban land use are key ecological drivers of both virus richness and transmission centrality, and cross-order sharing is higher among orders such as carnivores and artiodactyls, enabling refined surveillance prioritization.