The coronavirus that is circulating around the world may have close relatives that have yet to be discovered, a clue that the current pandemic will not be the last to threaten humans.
New research published Tuesday in the journal Nature Microbiology finds that the current strain, known in the scientific literature as SARS-CoV-2, genetically diverged from other known viruses circulating in bats 40 to 70 years ago.
Because coronaviruses frequently recombine and evolve into new species, other strains almost certainly have evolved within bat populations in China during those intervening years. That means that other viruses more closely related to SARS-CoV-2 than their current closest known relative may present the possibility of future outbreaks.
“From this ancestor in the 1960s and 1970s, there are probably other descendants, there are probably other lineages that have existed and circulated silently in bats for the past 40, 50 or 60 years,” said Maciej Boni, a biologist at the Center for Infectious disease dynamics at Penn State and co-author of the study. “This means that there will probably be another coronavirus pandemic. Whether it happens in 2025 or 2075, no one knows. “
The research found that while the SARS-CoV-2 virus can also infect pangolins, mammals native to China, Southeast Asia, and sub-Saharan Africa, the virus was likely transmitted to humans directly from a bat.
“There is no evidence that pangolins are facilitating adaptation to humans,” the researchers wrote.
SARS-CoV-2 is a sarbecovirus, a subgenus in the coronavirus family that also includes SARS, another virus that caused severe respiratory disease in humans. The virus that is most closely related to SARS-CoV-2, known as RaTG13, was identified in horseshoe bats in China’s Yunnan province in 2013.
Research shows that the two viruses are approximately 96 percent similar. Evolutionarily speaking, that 4 percent gap is a genetic gulf; There is less difference between humans and orangutans than between the two viruses.
What makes SARS-CoV-2, and any of its relatives yet to be discovered, dangerous to humans is that its spike protein combines with ACE-2 receptors, which exist in cells of the lower respiratory tract. Those cells become infected, spread the virus, and cause COVID-19, which has so far killed more than 140,000 people in the United States.
Researchers are unlikely to conclusively identify an index case, the first person infected with a bat coronavirus, likely sometime in November 2019. But further research on bat populations worldwide is likely to uncover some of the close relatives of the current virus, Boni said.
“We will never find the first case, but it is likely that with better sampling we will find bat lineages that perhaps in 2010 or 2015 circulated in bats but were very similar to the current SARS-2 virus,” he said. . “The more samples we make, the more likely we are to find a newer bat virus.”
The researchers called for an international surveillance network, both of bat populations worldwide and of humans that could contract new viruses. Past research has been limited to a few scientists studying some populations of bats, the surveillance Boni said is insufficient to fully capture the true number of potentially harmful pathogens that could spread to humans.
“Of course, it is a monumental task to start taking samples of tens of thousands of bats and characterize all of their viruses,” Boni said. “When you try to catch something that is emerging from an animal population to a human population, you need surveillance on both sides.”
“It has to be coordinated internationally. It cannot be a fragmentary effort, ”he said.