Is there a link between environmental change and virus spillover (i.e. the passage of viruses from animals to humans)? This is one of the most frequently-asked questions in these weeks of the coronavirus emergency – questions that are often given answers that have no scientific basis, in both a negative and a positive sense.
To respond to fake news and provide reliable data, researchers from the University of California, Davis campus, who are taking part in a major project entitled PREDICT on emerging diseases, used mathematical models to analyze the link between 142 viruses that have spilled over (SARS, Ebola, Marburg, Nipah, etc.) and the species that have been indicated as potential hosts, taking into account the environmental and climate conditions in which the passage from animal species to humans occurred. The researchers used the Red List of the International Union for Conservation of Nature (IUCN), the biggest archive of the situation of animal and plant species on Earth, as a main source. And in the end they found convincing proof of the fact that the environmental changes caused by humans plays a vital role.
“Spillover of viruses from animals is a direct result of our actions involving wildlife and their habitat,” said Christine Kreuder Johnson, project director of PREDICT and lead author of the study, “These actions simultaneously threaten species survival and increase the risk of spillover. In an unfortunate convergence of many factors, this brings about the kind of mess we’re in now.”
The researchers published the results of their work in the scientific journal Proceedings of the Royal Society B.
The expansion of human activity – they write – has pushed many wild animal species to try to adapt to new situations, such as various types of rodents, bats and primates with their hundreds of viruses, which now live near farms or cities.
At the other end of the spectrum, the species that have not managed to adapt to the continuous enlargement of human activity (and that, in many cases, are also decimated by illegal hunting) often find themselves in very precarious conditions and at risk of extinction. Paradoxically, however, even these animals (carriers of particularly high numbers of viruses, for various reasons) become a vehicle for spillover, because they are monitored closely and can infect the people that are trying to keep them under control (if, on the other hand, these animals were to follow their natural destiny, they would have very little contact with human beings and the risk of virus transmission would be minimal).
We must keep this information in mind once this emergency is over, when we are called upon to plan a different future in order to prevent pandemics like SARS and COVID-19 from reappearing regularly.