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Humans are more dangerous to animals than the latter to the former. Researchers discovered that we pass twice as many viruses we receive from domestic and wild animals than we receive.
Humans Pose More Dangers to Animals
In a new study, researchers analyze viral genomes and it shows that humans are significantly more dangerous to other species than they are to us. Researchers found the viral families that potentially infect human bodies out of the 32 that were taken into consideration.
When the frequency of leaps between species was counted, anthroponotic infection -- the frequency of jumps from humans to other animals -- accounted for 64% of the jumps. It makes sense that our viruses spread so extensively because humans have adapted to live in such a diverse range of habitats.
"Our population size is huge. And our global distribution is basically everywhere," University College London geneticist Cedric Tan told Michael Le Page.
If a virus that people carry infects a different animal species, it may survive human eradication or even develop new adaptations before reentering the human population.
These results are corroborated by earlier studies. Although over 1.6 million animal viruses exist, less than 0.1 percent of these viruses originate from other species and have been reported to infect humans.
However, as the COVID-19 pandemic has shown, it only takes one virus to cause devastation. Tan and associates also discovered characteristics that may indicate a virus's propensity to spread to humans.
In comparison to viruses that already infect a wider range of hosts, they discovered that viruses that are more likely to leap species showed an accelerated rate of genetic modifications. Their rates of mutation were lower.
According to the researchers, generalist viruses must be taking advantage of traits that more species have in common, such as the ACE2 host-cell receptor that all vertebrates have and that COVID-19 employs. Most likely, the animals with whom we come into contact are most at risk from these infections.
"Large gaps in the genomic surveillance of viruses thus far suggest that we have only just scratched the surface of the true viral diversity in nature," Tan and his colleagues wrote. "Overall, our results highlight the importance of surveying and monitoring human-to-animal transmission of viruses, and its impacts on human and animal health."
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What Is Spillover Theory?
At first, scientists believed spillovers to be uncommon occurrences. But an increasing number of research indicate otherwise --they occur often.
For example, COVID-19 started off in an animal and "spilled over" into humans.
Animal viruses typically don't leave their host. The transmission of a virus has been likened by scientists to winning the lottery -- it only has to be at the right place at the right moment and have unique, uncommon qualities to infect humans. The simultaneous occurrence of all three phenomena is quite uncommon.
The spillover theory has affected how researchers look for novel infections or identify the ones that may start pandemics in the future. It specifically prompted scientists to focus their attention on finding novel viruses in wild animals.
Since 2009, the federal government of the United States of America has invested hundreds of millions of dollars in the catching of wild animals like bats and rats, cataloging all the viruses that are present in their bodies, and then trying to determine which of these viruses is most likely to create an expensive human outbreak or pandemic. Regretfully, this endeavor was unable to identify SARS-CoV-2 before the infection spread around the world.
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