New study suggests early COVID-19 strain spread from bats by wildlife trade

Yahoo

07-05-2025

Above: Nexstar Media Wire video on the differences between COVID, RSV, strep and the flu.
SAN DIEGO (FOX 5/KUSI) — A recent study from an international team of researchers, including those from UC San Diego's School of Medicine, gives new credence to the theory that the COVID-19 pandemic spread naturally by way of wild mammal trade, as opposed to a lab leak.
The study, which was published in the science journal Cell on Wednesday, examined the evolution of the COVID-19 virus — SARS-CoV-2 — and compared it to a coronavirus behind an earlier outbreak, the 2002 SARS pandemic.
Using genome sequencing to map the histories of these and more than 250 coronaviruses, the scientists found a number parallels in the evolution of the viruses behind SARS and COVID that suggest the two shared a similar mode of dispersal.
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These findings, in their view, dispute the contested theory that COVID originated from a lab leak, even as the Trump administration and Congressional Republicans have ratcheted up promotion of supposition in recent months.
The ancestors of both viruses, the study says, had circulated in horseshoe bats across much of China and other countries in southeast Asia for millennia, mutating as it interacted with other coronaviruses inside the cells of its host.
This genetic mixing, which is called recombination, creates new variations of the virus, each more potent until it reaches the point where it can become a human pathogen.
The closest ancestor identified by the study to SARS and COVID reached that tipping point only a few years before it was reported by humans — about one to two years before SARS was first detected in Guangdong Province and five to seven years before COVID emerged in Wuhan.
However, the distance between the origin of this viral ancestor and where the pandemics began was too far to have been carried just by bats. Instead, the study says these viruses spilled over into other wild animals, which were unwittingly carried hundreds of miles by traders.
The consensus among researchers of the earlier SARS pandemic has generally agreed this is how the virus reached Guangdong relatively quickly, most likely having hitched a ride to animals like palm civets or raccoon dogs commonly traded for their fur and meat.
That patten of zoonotic spread, the new study argues, bolsters the plausibility that SARS-CoV2 reached Wuhan from southwest China in the same manner.
'For more than two decades the scientific community has concluded that the live-wildlife trade was how those hundreds of miles were covered,' said Dr. Michael Worobey, the head of the Department of Ecology and Evolutionary Biology at the University of Arizona who served as a co-senior author on the study. 'We're seeing exactly the same pattern with SARS-CoV-2.'
The researchers point to an earlier study they conducted that traced human transmission of COVID-19 back to the Huanan Seafood Market in Wuhan, where many wild mammals are sold by traders, as further evidence for natural zoonotic spillover.
'At the outset of the COVID-19 pandemic, there was a concern that the distance between Wuhan and the bat virus reservoir was too extreme for a zoonotic origin,' said Dr. Joel Wertheim, a professor of medicine at UCSD School of Medicine's Division of Infectious Diseases and Global Public Health and a co-senior author of the study.
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'This paper shows that it isn't unusual and is, in fact, extremely similar to the emergence of SARS-CoV-1 in 2002,' he continued.
That said, proponents of the lab leak theory have pointed to this distance as proof of their explanation of COVID's early spread, arguing it must have been human intervention in the form of scientists that transported the coronavirus from southwest China to Wuhan.
However, no evidence has been provided that an earlier strain virus was in fact at the the Wuhan Institute of Virology, the lab at the center of the theory, before the pandemic.
While researchers concede the debate on COVID's origins may in all likelihood remain unsettled, the study's authors say their findings remain notable, giving researchers additional insight into a possible future coronavirus outbreak.
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