By Anna Kuchment
04:00 on July 28, 2020 CDT
Close relatives of the virus that causes COVID-19 to probably circulate in bats for decades before the viruses gave the impression on humans last year, triggering the world’s worst pandemic in more than a hundred years, according to a study published Tuesday.
The article, co-written through Todd Castoe, a researcher at the University of Texas at Arlington, and published in the journal Nature Microbiology, also found no evidence that the virus was manufactured or released through a laboratory in Wuhan, China, as some have done. Speculated.
“Since the 1960s or 1970s, these viruses have been circulating undetected in bats, probably in a position to infect humans at any time,” said Maciej Boni, the paper’s director and infectious disease expert at Pennsylvania State University. “We’ve been unlucky in 2019.”
Scientists still know precisely how the new coronavirus first spread to humans, but the study suggests that bats were the main reservoir of the virus.
So far, researchers have hypothesized that the virus may come from dogs, snakes, bats or pangolins, highly manipulated mammals that look like armadillos. Some have warned that it was created in a Wuhan lab as a biological weapon or that it was accidentally left a lab.
“The document does a smart job in removing some of the remaining questions about the origin of this virus,” said Robert Garry of Tulane University School of Medicine, who was not involved in the study.
By comparing the SARS-CoV-2 virus with its cousins in bats, pangolins and other animals, scientists were able to demonstrate that it is approximately 96% similar to its closest known bat virus relative. They then tested the genetic clothing of SARS-CoV-2 to estimate when it would possibly have deviated from this nearest known relative.
“We know how mutations temporarily accumulate in this virus,” said Castoe, a genetics expert at UTA. “And we can use it as a kind of molecular clock.” The more mutations the virus has, the more it evolves along its own branch of the relative circle tree.
They found that the tree branch of the circle of relatives that gave birth to SARS-CoV-2 was indifferent to its nearest known bat virus 3 decades ago or more. The examination indicated that close relatives of SARS-CoV-2 may have sprung up as early as the 1940s.
Castoe said it was probably the lack of opportunities that prevented viruses from jumping earlier in humans. As the world’s population grows and humans continue to move to undeveloped areas of the past, humans and animals interact more frequently.
This early origin, Castoe said, makes it even less likely than the virus synthesized in a lab.
And if it were an herbal virus stored in a lab for study purposes and released by accident, one would expect several lab staff members to have fallen ill, which happened, Boni said.
Castoe added that the recombinations it observed in the virus, fragments of RNA that the virus has exchanged with other viruses, are not other than what it sees in the wild. “This article shows that recombination happens all the time in nature,” he says. “It’s a hundred percent overall for the course.”
The long-standing discrepancy with recently known bat viruses also indicates that there could possibly be SARS-CoV-2-like viruses circulating in bats, waiting for their chance to infect humans.
Scientists have long known that bats bring a wide range of diseases. SARS and MERS, two other coronavirus diseases that cause pneumonia in humans, have been linked to bats, as have Ebola.
It also suggests that because viruses constantly mutate and replace, it will be difficult to identify viruses that can cause primary human epidemics before they emerge from animals like bats. This underscores the need for real-time human disease surveillance systems that can temporarily identify new viruses.
This article is another sign that humans and bats might want to distance themselves socially. In many countries, other people hunt bats and buy them alive in markets. “Let’s reduce or not use bats as food,” Garry said.
It also recommends strengthening virus surveillance in bats so that we can move several steps toward the next coronavirus pandemic.