Almost two years after the start of the COVID-19 pandemic, the origin of the virus that is plaguing the world remains shrouded in mystery.
Most scientists believe it emerged in the wild and passed from bats to humans, either directly or through another animal. Others believe he escaped from a Chinese lab.
Now, with the worldwide COVID-19 death toll surpassing 5.2 million on the second anniversary of the first human cases, a growing number of scientists are trying to focus on what they consider most plausible “zoonotic,” or animal-to-human, theory, in the hope that what is learned will help humanity fend off new viruses and variants.
“The lab leak scenario gets a lot of attention, you know, on places like Twitter,” but “there’s no evidence that this virus was in a lab,” said Stephen Goldstein, scientist at the University of Utah, who along with 20 others wrote an article in the journal Cell in August presenting evidence of animal origin.
Michael Worobey, an evolutionary biologist from the University of Arizona who contributed to the article, said he always thought zoonotic transmission was more likely than a lab leak, but signed a letter with other scientists last spring saying both theories were viable. Since then, he said, his own research and that of others have made him even more confident about the animal hypothesis, which is “just a lot more supported by the data.”
Last month, Worobey released a COVID-19 timeline linking the first known human case to the Huanan Seafood Wholesale Market in Wuhan, China, where live animals were sold.
“The idea of the lab leak is almost certainly a huge distraction that distracts from what really happened,” he said.
Others are not so sure. Over the summer, a review ordered by President Joe Biden showed that four U.S. intelligence agencies believed with low confidence that the virus was initially transmitted from animal to human, and one agency believed with low confidence. moderate that the first infection was laboratory-related. .
Some proponents of the laboratory leak hypothesis have speculated that the researchers were accidentally exposed due to inadequate safety practices when working with samples from nature, or perhaps after creating the virus in laboratory. U.S. intelligence officials have dismissed suspicions that China has developed the virus as a biological weapon.
The continued search for answers has exacerbated tensions between the United States and China, which accused the United States of making it the scapegoat for the disaster. Some experts fear the origins of the pandemic will never be known.
From bats to humans
Scientists said in Cell’s article that SARS-CoV-2, which causes COVID-19, is the ninth coronavirus documented to infect humans. All the previous ones came from animals.
This includes the virus that caused the 2003 SARS outbreak, which has also been linked to markets selling live animals in China.
Many researchers believe the wild animals were intermediate hosts for SARS-CoV-2, meaning they were infected with a bat coronavirus which later evolved. Scientists searched for the exact bat coronavirus involved, and in September they identified three viruses in bats in Laos more similar to SARS-CoV-2 than any known virus.
Worobey suspects raccoon dogs as the intermediate host. The fox-like mammals are susceptible to coronaviruses and were sold live in the Huanan market, he said.
“The gold standard for an animal origin” would be an infected animal from there, Goldstein said. “But as far as we know, the market has been gutted.”
Earlier this year, a joint report by the World Health Organization and China characterized transmission of the virus from bats to humans through another animal as the most likely scenario and an “extremely unlikely” laboratory leak.
But this report also sowed doubt by attributing the first known case of COVID-19 to an accountant unrelated to the Huanan market and who first showed symptoms on December 8, 2019. Worobey said that supporters of the theory of laboratory leaks point to this case. claiming that the virus escaped from a facility at the Wuhan Institute of Virology near where the man lived.
According to Worobey’s research, however, the man said in an interview that his Dec. 8 illness was actually a dental issue, and his COVID-19 symptoms began on Dec. 16, a date confirmed in the records of the ‘hospital.
Worobey’s analysis identifies an earlier case: a seller in the Huanan market who contracted COVID-19 on December 11.
Experts fear the same kind of virus transmission from animal to human could trigger new pandemics – and make this one worse.
Since the emergence of COVID-19, many types of animals have been infected, including cats, dogs and ferrets; zoo animals such as big cats, otters and non-human primates; farmed mink; and white-tailed deer.
Most have contracted the virus from humans, according to the United States Centers for Disease Control and Prevention, which says humans can pass it to animals through close contact, but the risk of animals passing it to humans is low. .
Another fear, however, is that the animals could release new viral variants. Some wonder if the omicron variant started out this way.
“All over the world, we could have animals that potentially incubate these variants even though we have (COVID-19) under control in humans,” said David O’Connor, a virology expert at the University of Wisconsin-Madison. “We’re probably not going to start a big giraffe vaccination program anytime soon. “
Worobey said he was looking for DNA fingerprints that could indicate whether the omicron was created when the virus passed from humans to animals, mutated and then returned to humans.
Experts say preventing zoonoses will require not only tackling illegal sales of wild animals, but also making progress on major global issues that increase human-animal contact at risk, such as habitat destruction and climate change.
Failure to fully investigate the animal origin of the virus, the scientists said in Cell’s article, “it would leave the world vulnerable to future pandemics resulting from the same human activities that have repeatedly put us on a path of death. collision with new viruses “.
But further investigation is hampered by superpower politics. Lawrence Gostin of Georgetown University said there had been an “unarmed fight” between China and the United States.
“The politics around the origins inquiry has literally poisoned the well of global cooperation,” said Gostin, director of the WHO Collaborating Center on National and Global Health Law. “The politics have literally been toxic.”
A PA investigation last year found that the Chinese government strictly controls all research into the origins of COVID-19 and promotes marginal theories that the virus may have originated outside the country.
“It is a country that is by instinct very closed, and it was never going to allow unhindered access of foreigners to its territory,” said Gostin.
Still, Gostin said there is one positive development that emerged from the investigation: The WHO formed an advisory group to examine the origins of the pandemic.
And Gostin said that if he doubts the panel will solve the mystery, “they will have a group of highly trained scientists ready to be deployed in an instant during the next pandemic.”