While the exact origin of the coronavirus remains unclear, scientists have run to determine how it went from animals to humans so that they can prevent another pandemic.
The next one may be just a matter of time, suggests a new study.
The authors said that a virus with a similar ability to infect humans may already be out there, carried by a type of bat known to have horseshoe-shaped “leaves” on its nose.
Scientists made this prediction after building a coronavirus family tree ̵
The lineage of the virus causing covid-19 appears to have branched out from its closest viral relatives some 40-70 years ago, the authors wrote this week in Nature Microbiology. And other viruses in the same branch of the family likely share a similar ability to attach to human airway cells, said Maciej F. Boni, a biologist at Pennsylvania State University and lead author of the study.
“It is very likely that there are many other lines that nobody is aware of, because nobody has tried, that circulate silently in bats,” he said. “Potentially everyone could have this ability to infect human cells.”
Tracing virus family trees is a challenge, as microbes mutate and swap sections of their genomes in ways that make it difficult to tell what happened when.
Coronaviruses, in particular, are prone to this type of recombination, in part because a bat can carry multiple types simultaneously. A virus inside a bat can easily collect genetic code fragments from other viruses that infect the same animal – let’s say, by grabbing instructions to hook up to human cells from a source, while collecting the code to penetrate cell membranes from a other.
However, using a range of statistical techniques, scientists identified three genetic regions in the coronavirus that appeared to have remained intact for decades. They identified the same three regions in another coronavirus that came from a mace found in Yunnan, a province in southern China near Laos.
That virus cannot infect humans, but is otherwise very similar to the one causing the pandemic, which was first identified in human patients in the city of Wuhan. The two viruses appear to have branched into the family tree in the 1960s and have almost certainly discovered cousins with the potential to infect humans, said Boni, who has collaborated with scientists in Europe and China.
The research represents a valuable advance in tracing the origin of the coronavirus responsible for covid-19, said Alina Chan, a molecular biologist at the Broad Institute in Cambridge, Massachusetts who was not involved in the study.
“They narrowed it down,” he said.
A good way to hunt the cousins of these two coronaviruses would be to take samples from bats over the hundreds of miles between Yunnan and Wuhan, said Boni, a member of Penn State’s Center for Infectious Disease Dynamics. This could guide strategies to prevent such viruses from “jumping” from the bat to humans in the future, perhaps by identifying live animal markets where better hygiene measures could be implemented.
The coronavirus responsible for covid-19 was initially thought to have passed from one animal to another in a similar market in Wuhan, but Chinese officials later discounted that possibility, as some of the early patients had no apparent connection to that market. . Since then, scientists have speculated that the fateful transmission occurred in some other market. US intelligence officials have suggested that it may have been accidentally released in a research laboratory, but virologists from academia are generally skeptical of that theory.
By itself, the presence of similar coronaviruses in bats would not mean that another pandemic is imminent, said Kevin Olival, vice president of research at EcoHealth Alliance, a nonprofit organization that works with scientists around the world to protect people and animals from infectious diseases.
The size and range of the relevant bat population and the behavior of humans are also part of the equation.
“To calculate the risk, you have to put all those pieces together,” he said.
Among the countries where the nonprofit has collaborated with local scientists to sample bat populations is China, although U.S. funding for that collaboration has been suspended by the Trump administration, with officials citing the virus theory released by a Chinese laboratory. More than 70 Nobel laureates have reported the move.
What is not in question is that viruses have jumped from animals to humans for centuries and will happen again.
And coronaviruses carried by bats are the main suspects.
Similar predictions have been made previously – as in 2013, when an article in the journal Science was titled “Bats could lead to the next SARS pandemic.”
Sure enough, as the world now knows too well, that it has come true.
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