Researchers concluded that the virus evolved for decades in bats, not pangolins.
A team of European, Chinese, and American scientists has discovered the lineage that gave rise to Sars-CoV-2, responsible for the Covid-19 pandemic. The study was published this week in the journal Nature Microbiology.
Analyzing the evolutionary history of the new coronavirus, researchers concluded that the lineage of the microorganism evolved over decades in bats and probably includes traces of other viruses that infect humans.
“Coronaviruses have genetic material that is highly recombinant, meaning different regions of the virus’s genome can be derived from multiple sources,” said Maciej Boni, associate professor of biology at Pennsylvania State University, and a co-author of the study. “This has made it difficult to reconstruct SARS-CoV-2’s origins. You have to identify all the regions that have been recombining and trace their histories.”
By analyzing the genome thoroughly, scientists were able to reconstruct the evolutionary connections between Sars-CoV-2 and its “relatives” known to affect bats and pangolins.
The researchers found that the lineage of the microorganism was already detected in bats between 40 and 70 years ago.
Although the new coronavirus is similar to RaTG13, found in bats in China in 2013, it diverged from viruses detected in these animals in 1969, taking another evolutionary path.
The team found that one of the oldest characteristics that Sars-CoV-2 shares with its relatives is the receptor-binding domain (RBD), which is located on the spike protein and allows the virus to recognize and bind to human cells.
According to the scientists, this means that other viruses capable of infecting humans are circulating in bats in China and suggests that associating evolutionary changes in the microorganism with pangolins is a mistake.
“While it is possible that pangolins may have acted as an intermediate host facilitating transmission of SARS-CoV-2 to humans, no evidence exists to suggest that pangolin infection is a requirement for bat viruses to cross into humans,” explained David L. Robertson, co-author of the study and professor of computational virology at the MRC-University of Glasgow Center for Virus Research in Scotland. “Instead, our research suggests that SARS-CoV-2 likely evolved the ability to replicate in the upper respiratory tract of both humans and pangolins.”
Scientists believe that to prevent future pandemics it is necessary to further study microorganisms that affect other animals, especially bats.
“We were too late in responding to the initial SARS-CoV-2 outbreak, but this will not be our last coronavirus pandemic,” Maciej Boni said. “A much more comprehensive and real-time surveillance system needs to be put in place to catch viruses like this when case numbers are still in the double digits.”