Global shifts in mammalian population trends reveal key predictors of virus spillover risk

• Exploitation of wildlife and loss of natural habitat are key drivers in the emergence of zoonotic diseases that spread from wildlife to humans.

• ❯  As human populations continue to expand, requiring more land (habitat destruction) and greater food resources (agriculture, wildlife hunting, wildlife trade), human-animal interactions will continue to increase, and the corresponding emergence of zoonotic viruses will also increase — exposing humans to a greater number of pathogens with pandemic potential, such as the current COVID-19 pandemic.
  
  ❯  Large-scale human encroachment into wildlife habitat has resulted in wildlife movement and increased human contact with wild animals, heightening rates of virus spillover, creating losses in species abundance, and, for many species, threatening them with extinction. Movement and redistribution of wildlife often enhance disease spread in wildlife populations, resulting in epidemics in wildlife and increased risk of spillover to humans when these epidemics are at their peak, especially if wildlife have relocated close to human communities.
  
  ❯  Loss of biodiversity from over-exploitation and deforestation increases viral spillover risk, not only as humans interact more directly with wildlife, but also because losing species diversity can favor a higher abundance of some species that are especially well adapted to zoonotic viruses.

• Domesticated animals had a higher number of zoonotic viruses per species, which is a consequence of their global abundance and the very close interactions people have had with domesticated species over centuries.

• ❯  Humans have a long history of close interaction with domesticated species, resulting in shared viruses.
  
  ❯  Domestic animals can also amplify infections as an intermediary for transmission of viruses from wildlife to humans.

• Wildlife species which have adapted well to human-modified habitats frequently carry zoonotic viruses and have increased potential for interactions with humans that facilitate disease transfer.

• ❯  Wild animal species that have been best able to adapt to human-altered landscapes (e.g., rats and mice, rhesus macaques living in urban environments) are more likely to have close contact with humans, increasing the likelihood of viral spillover.

Zoonotic Viruses in Threatened Taxa

Number of mammalian viruses shared with humans for each taxonomic order by IUCN threatened species criteria. 

Network of Mammalian Species and their Zoonotic Viruses

Bipartite network showing wild and domesticated mammalian species and their zoonotic virus associations. Host species harboring the same zoonotic virus are linked by the viruses they share.