(CN) — The Huanan Seafood Wholesale Market in Wuhan, China, recently gained global notoriety as ground zero where a novel coronavirus may have leapt from pangolins to humans. Now new research pinpoints other animals and environments in which humans are at high risk of contracting zoonotic viruses.
"Spillover of viruses from animals is a direct result of our actions involving wildlife and their habitat," said the study’s lead author Christine Kreuder Johnson, project director of USAID PREDICT in a statement. "The consequence is they're sharing their viruses with us. 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.”
While many questions remain about how a disease leaps from species to species, most emerging infection diseases that threaten humans make this leap, therefore our lives may very well depend on understanding this problem.
In order to generate general warning signs of virus spillover, half a dozen American and Australian researchers contextualized the International Union for Conservation of Nature's Red List of Threatened Species with data on all known zoonotic diseases in land animals.
They analyzed 142 viruses, of which 139 infected land mammals. The analysis is of course limited to available data, which tends to be biased towards diseases found to have strong symptoms and infect people in developed areas, since diseases with minor symptoms or infecting people in areas with poor healthcare systems are unlikely to be reported.
Eleven percent of the 5,335 mammals studied carry zoonotic viruses, and though most animals only carry one zoonotic virus, bats, rodents, and primates carry 75% of known zoonotic viruses. Higher species diversity lends itself to higher virus diversity. While nearly 87% of mammals in the literature are not reported to carry zoonotic diseases, a lack of data should not be taken as proof that they are not there.
Generally speaking, zoonotic viruses were found to be most common in mammals that are at the least threatened but growing in population size. In fact, these mammals carry 1.5 times the number of zoonotic diseases compared to animals with stable populations.
Among threatened species, the most zoonotic diseases were found among animals with a reduced population size "owing to exploitation," which researchers attribute to the increased interaction between animals and the humans who hunt and traffic them.
Of eight taxa identified for risks of zoonotic viruses, the Pilosa group of sloths and anteaters was last on the short list, but notably there.
Domesticated animals, which interact the most with human, carry an average of 19 zoonotic diseases, compared to wild species which might carry one.
High-risk activities driving rises in infectious disease also drive species extinction and wildlife declines, including the "domestication of animals, human encroachment into habitats high in wildlife biodiversity and hunting of wild animals."
"We need to be really attentive to how we interact with wildlife and the activities that bring humans and wildlife together," Johnson cautioned. "We obviously don't want pandemics of this scale. We need to find ways to co-exist safely with wildlife, as they have no shortages of viruses to give us."
This research warning against the risks of viruses leaping from animals to humans was first submitted for publication in November, well before the outbreak of Covid-19. It was published Tuesday in the journal Proceedings of the Royal Society B.
This timely project was funded by the National Institute of Health and the USAID Emerging Pandemic Threat PREDICT program.
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