Study: Coronavirus may have been in humans for years
The research poses some intriguing possibilities with respect to the origin of the current coronavirus. One of the possibilities indicates that the virus could have spread harmlessly among human societies for quite some time before it became the pandemic that has halted the world in its tracks.
“It is possible that a progenitor of SARS-CoV-2 jumped into humans, acquiring through adaptation during undetected human-to-human transmission,” the team from the US, UK, and Australia writes in the study.
“Once acquired, these adaptations would enable the pandemic to take off and produce a sufficiently large cluster of cases.”
The researchers analysed genomic data available from SARS-CoV-2 and other similar coronaviruses, showing that the receptor-binding domain (RBD) sections of SARS-CoV-2 spike proteins were so effective at binding to human cells, they had to be caused by natural selection.
“By comparing the available genome sequence data for known coronavirus strains, we can firmly determine that SARS-CoV-2 originated through natural processes,” said one of the researchers, immunologist Kristian Andersen at Scripps Research.
“Two features of the virus, the mutations in the RBD portion of the spike protein and its distinct backbone, rules out laboratory manipulation as a potential origin for SARS-CoV-2.”
With ‘laboratory experiment gone wrong’ out of the way, the team explored two viable hypotheses. First, that the natural selection occurred in an animal host before the virus was transmitted to humans. The team explains that although samples of coronaviruses in bats and pangolins have shown similar genomes, none of them fit perfectly just yet.
“Although no animal coronavirus has been identified that is sufficiently similar to have served as the direct progenitor of SARS-CoV-2, the diversity of coronaviruses in bats and other species is massively undersampled,” the researchers write.
The second hypothesis is that the natural selection happened in humans—after the virus was transmitted from an animal host.
“The second scenario is that the new coronavirus crossed from animals into humans before it became capable of causing human disease,” director of the National Institute of Health, Francis Collins explains on the NIH blog.