A month-long assessment in Wuhan sought the human origin of SARS-CoV-2. The investigators graded 4 possible scenarios.
A to-be-published joint study from the World Health Organization (WHO) and China states that transmission of SARS-CoV-2 from bats to humans most likely occurred through another animal.
The findings, which contribute toward an interpretation of COVID-19’s origins, also state that it is “extremely unlikely” the pandemic virus occurred through a laboratory leak—a popular theory held among leadership outside of China at the beginning of the outbreak.
The report, acquired as a draft by the Associated Press, is largely based on a WHO investigator visit to Wuhan from mid-January to mid-February this year. The investigators detailed 4 scenarios by which SARS-CoV-2 could have emerged, listed in order of most likelihood to least:
As the report draft explains, the evolutionary distance between bat-based coronaviruses and SARS-CoV-2 is estimated to be several decades, “suggesting a missing link.”
The WHO-led expedition to the original outbreak epicenter, as detailed previously in a podcast by HCPLive and the American Lung Association (ALA), speaks to the gap of knowledge still missing in understanding how the pandemic began, and what means were capable of preventing it.
As Donald Alcendor, PhD, vaccinologist and immunologist from Meharry Medical College and Vanderbilt University School of Medicine, explained in the podcast, the zoological intermediary to human transmission is still just a prediction.
“We know this is a zoological transmission,” Alcendor explained. “We have to understand how this virus is being transmitted in the animals that service reservoirs. And once we do, we need to limit this zoological contact to humans.”
Alcendor’s suggestion that pangolins—better known as scaly anteaters—may be involved in the SARS-CoV-2 human origin was supported by the WHO report, which noted the mammals have been observed with highly similar viruses. The report also suggested that mink and cats could have served as the intermediary, as both species carry COVID-19.
That said, the report did not draw conclusion on the belief that the outbreak began at a Wuhan seafood market—which sold a range of animal products, from bamboo rats and deer, to even live crocodiles—that reported a case cluster in December 2019. Previous cases observed outside the area of the market suggest the outbreak began elsewhere.
“No firm conclusion therefore about the role of the Huanan market in the origin of the outbreak, or how the infection was introduced into the market, can currently be drawn,” investigators wrote.
Peter Ben Embarek, a food scientist and WHO expert leading the Wuhan assessment, told AP on Friday the report was finalized and awaiting public release.