Kevin J. Olival et al recently published an article in Nature demonstrating their new analytical tool which could predict the next infectious disease outbreak in humans. Zoonotic diseases are those which can be transmitted from wild animals to humans, and are of great concern in recent times. Diseases like HIV, SARS, and Ebola are all examples of zoonotic diseases. Olival et al set out to understand which species of mammals are likely to harbor the next human virus and which viruses are likely to make the cross-species jump.
The research conducted by Olival and his colleagues is especially important because, to date, there has been no analysis conducted on the viral sharing between humans and other mammals. Olival et al created and analyzed a database of 2,805 mammal-viral associations including 754 mammal species and 586 unique viral species. They predicted the proportion of zoonotic viruses by comparing the phylogenetic relatedness of each mammal species to Homo sapiens and measuring how likely each species was to interact with people based on their geographical distribution and behavior.
They found that bats harbor a significantly higher level of zoonotic viruses than all other mammalian orders, which is not surprising considering we are already aware that SARS, Ebola, and rabies virus are bat-borne diseases. Researchers also concluded that the places most at risk for an emerging bat virus are the Amazonian and Orinoco rain forests as well as the Caribbean coast of South America.
Researchers hypothesized that “the number of viruses a given mammal species shares with humans [will increase] with phylogenetic proximity to humans and with opportunity for human contact.” They found that the proportion of zoonotic viruses does in fact increase with phylogenetic proximity to humans, and their analysis provided the first data to prove this. They were also able to show that increasing urbanization raises the risk of zoonotic spillover, as does increasing human population density. This is especially important now, since overpopulation is forcing more and more people to crowd into cities.
The researchers were able to create heat maps showing where there are large numbers of mammal species lacking information on viral diversity. Olival et al mention that such maps can be used by the Global Virome Project to allocate resources effectively to further their goal of discovering new viruses.
Olival, Kevin J. et al. “Host and viral traits predict zoonotic spillover from mammals.” Nature, vol. 546, no. 7660, 2017, pp. 646-65.