Fresh look at earliest COVID cases points to live-animal market as most likely source

Conspiracy theorists need little more than suspicion, some cherry-picked facts and vibrant imaginations to spin tales about the origins of the COVID-19 pandemic. For scientists trying to find the truth, however, it is more difficult.

Their search will lead them through a wealth of medical records, whose quotidian information will serve as an important guide to the circumstances and time of the coronavirus’ birth as a human disease. It will also matter if patients can recall their contact information and whereabouts.

But even though the Chinese government is willing to share all of its patient files with international investigators, it isn’t. Symptom reports and patients memories can be faulty and confusing. As they piece together the story, researchers need to verify every fact.

University of Arizona evolutionary biologist Michael Worobey offers a down payment on such sleuthing in this week’s edition of the journal Science. Drawn from medical journal articles, the work of World Health Organization investigators, media reports and online accounts, Worobey’s reconstruction leaves many questions unanswered. It does provide a guideline for further investigation.

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Worobey has played an influential role. He was one of 18 scientists whose objections to a WHO report on the coronavirus’ origins reignited investigation into the possibility that it might have leaked from the Wuhan Institute of Virology.

Their letter was published in Science after the WHO declared it “likely to very likely” that the virus jumped to humans from animals, and “extremely unlikely” that it escaped from the government lab. The group demanded that “a proper investigation” be conducted to determine the truth of the matter, noting that both theories were “not given balanced consideration”.

Worobey stated at the time “both” explanations were “on the table for me.” However, his new work heavily favors the “animal spillover.”

Worobey is getting mixed reviews.

“I do not think that this will improve our collective understanding of the events,” stated Dr. David Relman ,, the Stanford microbiologist and organizer of the Science letter. Relman stated that Worobey’s narrative is largely composed of “third-and fourth-hand information.” It is inconsistent, fragmentary and possibly unreliable because it is based mainly on Worobey.

But Scripps Institution microbiologist Kristian Andersen, who has long argued that an animal spillover was more likely than a lab leak, lauded Worobey’s research for “uncovering several new key insights.”

The collective evidence “clearly points to the Huanan Market as a very likely source of the origin of the COVID-19 pandemic,” Andersen said.

Worobey’s account calls into question the date and location of the earliest reported case of the mysterious type of pneumonia that was later recognized as COVID-19. His research suggests it was not — as has been widely reported — a 41-year-old accountant with no connection to the Huanan Market, but a seafood vendor who worked there. A Chinese investigative reporter discovered that the Dec. 8 fever of the accountant was caused by an infection following dental surgery to remove retained child teeth. The accountant would go on to develop another fever eight days later that was a sign of COVID-19. )

A full 11 days before Chinese authorities focused their attention on the Huanan Market as the common link in the mysterious infections, doctors at two Wuhan hospitals had already identified 14 cases of the unexplained pneumonia. Eight patients spent time at the market where live raccoon dogs were being sold.

Casual observers of the origin debate would not see the significance of such fine details. They are important.

Those arguing that China has covered up an accidental lab leak or the intentional release of an engineered pathogen have seized upon this finding in the WHO report: Only 33% of 168 patients who developed the unexplained pneumonia early in the outbreak had a direct link to the Huanan Market. Even that figure is likely to be exaggerated by doctors who searched for links to the Huanan Market after Chinese authorities identified it as the probable source.

They’ve also made much of the now-disputed report that the earliest known patient (the 41-year-old accountant) lived nearly 20 miles south of the Huanan Market and had never been there, yet he showed up sick in a hospital close to the Wuhan Institute of Virology.

Dr. Marc Suchard ,, a UCLA researcher who uses genetic sequencing to study disease spread, stated that Worobey’s reconstruction shows that most early cases are located near the market. Suchard indicated that he hopes to continue working with Worobey in the next phase.

China believes that the SARS-CoV-2 viral disease was caused by a spillover. They responded quickly to reports of an unexplained illness in Wuhan and activated a national alert system.

They dismiss the possibility of the virus having escaped from the Wuhan laboratory for virology. They have been reluctant to share their records with WHO investigators. Skepticism has grown about the claims of the government, as it has failed to disclose past disasters.

Worobey didn’t acknowledge the political debate about the virus’ origins. He made it clear that his reconstruction of events strongly points to a spillover explanation.

For instance, by his accounting, 10 of the 19 earliest cases identified — 53% — had a link to the market. He said that doctors could not have inflated this number following the government’s lead because all of them were identified before authorities made any announcement.

“There was a genuine preponderance of early COVID-19 cases associated with Huanan Market,” Worobey wrote.

He also stated that the SARS-CoV-2 virus was well-known and that early cases had little to no connection with Huanan Market. People with no symptoms or few symptoms can spread the virus easily. A severe infection can progress in two weeks. Approximately 7% of the people who are infected end-up being hospitalized.

That means by the time people began to land in Wuhan’s hospitals, the virus had probably been circulating locally for weeks — and at least 93% of infected people were out and about, able to spread it in a city of 11 million.

Most patients who had no direct connection to the market lived nearby. Worobey stated that this “is remarkable and provides compelling evidence of community transmission began at the market.”

These facts suggest that the pandemic’s patient zero will not be found.

This person may have been dining with infected raccoons in their Huanan Market cages in the late November or earlyDecember. He or she might have been one of the nearly 50% of people who don’t feel very sick but are still quite effective at passing SARS-CoV-2 on.

The animal that incubated this virus is less likely to be discovered. Chinese researchers told WHO investigators they took samples from 188 animals from 18 species at the market, and all tested negative. And since the market was closed and disinfected on Jan. 1, 2020, there’s no way to look further. Researchers will continue to collect epidemiological data and analyze the details to get a complete picture of the virus’s birth.

Genetic sequencing data can also help, Worobey said. As the virus moves from person to person, its genetic signature changes just enough to reveal the order in which infections occurred. Geneticists and epidemiologists can create a family tree of infection if they have access to the same data.

As they cross-check genetic signatures and patient accounts about their contacts and whereabouts, they might be able timestamp certain infections and identify the patterns of early transmissions. This should bring them closer to the root tree of their family tree, although they may not be patient zero.

“Conclusive evidence of a Huanan Market origin from infected wildlife may nonetheless be obtainable,” Worobey wrote. “Preventing future pandemics depends on this effort.”

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