Predictive Map Identifies Which Species are Likely to Harbor the Next Human Virus

Want to know where the next infectious disease outbreak will come from? To paraphrase the popular saying, “There may be an app for that.” Sort of.

Researchers from the New York-based EcoHealth Alliance have developed a predictive “map” that identifies the zoonotic host species that are “likely to harbor the next human virus” and documents the regions of the world where they can be found. Their findings were published on June 23, 2017 in the journal Nature.

“Our article strives to tackle questions regarding zoonotic disease risk that haven’t been tackled extensively to date, including why these diseases are emerging and where they may emerge in the future,” Kevin J. Olival, PhD, associate vice president, research at EcoHealth Alliance told Contagion^®. “Emerging diseases make for great headlines because there is that fear factor. However, the fact is zoonotic diseases have been increasing from decade to decade, and we are seeing more of these events globally. The impact is real and the potential threat is real.”

The nonprofit EcoHealth Alliance bills itself as a global organization “working at the intersection of environmental, animal, and public health.” For the Nature project, which received funding as part of USAID’s Emerging Pandemic Threats PREDICT initiative, Dr. Olival, an ecologist and evolutionary biologist, and his colleagues created a database of the nearly 600 viruses that have been known to infect more than 750 mammal species. Using this database, they developed mathematical models to identify the characteristics of host species capable of transmitting these zoonotic viruses to humans.

Among other factors, the team found that zoonotic potential is predicted by how closely related the host species is to humans in terms of evolutionary development (“phylogenetic relatedness”), the taxonomic order the species belongs to, and the human population within the host species range, which they believe may convey the amount of possible human-to-wildlife contact. Overall, the team found that, among mammals, bats harbor the highest proportion of zoonotic viruses.

Based on bat population estimates, the EcoHealth Alliance researchers have identified South and Central America as well as parts of Asia as hotspots of so-called “missing zoonoses,” or currently undiscovered viruses that could be passed along to humans. Although these hotspots have been documented in color-coded heat-maps developed by the team, they emphasize that bats’ potential role as transmitters of viruses ultimately depends on the level of contact they have with humans—including any activity that alters their habitat (such as development) or disturbs their ecology (such as hunting).

The findings also document a similar potential role for primates in Central America, Africa, and Southeast Asia—and map areas of possible heightened risk for disease emergence and host-to-human transmission. In general, the authors believe that conservation efforts designed to protect potential host species can help reduce the risk for zoonotic disease, at least in part by serving to limit human-host interactions. Future projects by the EcoHealth Alliance team will involve targeting field surveillance efforts around the world to identify emerging disease threats in both animals and humans.

“While our paper is focused a bit more on the wildlife ecology side, and the understanding of diseases in the natural environment, we believe there is also a huge role for infectious disease specialists and clinicians in identifying potential disease threats and in hopefully mitigating risk,” Dr. Olival said. “In many places, we don’t know how often new diseases are spilling over into the human population, so we definitely need more surveillance efforts in communities and efforts to educate human populations about the potential risk. We see our work as providing a rough map of where we should pay attention to these zoonotic diseases, and where we may see them jump over into humans.”

Brian P. Dunleavy is a medical writer and editor based in New York. His work has appeared in numerous healthcare-related publications. He is the former editor of Infectious Disease Special Edition.