Two studies published Tuesday in the prestigious journal Science conclude that the COVID-19 pandemic began in the market from the city of Wuhan, China, thus pointing to a very probable animal origin of the virus.
The first study is a geographical analysis showing that the first cases detected in December 2019 were concentrated around the market. The second is a genomic analysis of the virus from the first cases demonstrating that it is very unlikely that the virus circulated widely in humans before November 2019.
Since the beginning of the pandemic, the debate has raged between experts, who are still trying to unravel the mystery of the origin of the virus almost three years later.
One of the authors of these studies himself, Michael Worobey, a virologist at the University of Arizona, had signed a 2021 letter calling for serious consideration of the hypothesis of a leak from a laboratory in Wuhan.< /p>
But the data analyzed since “has made me evolve, to the point that today I also think that it is simply not plausible that the virus was introduced in any way other than through trade of animals at the Wuhan market,” he said at a press conference.
For his part, Kristian Andersen, of the Scripps Research Institute and also co-author of these studies, said, “Have we disproved the lab leak theory? No. Can we do it one day? No. But I think it's important to understand that there are possible scenarios, and probable ones. And that ''possible'' does not mean 'just as likely'.”
Focus around the market
The first study analyzed the places of residence of the first 155 cases identified in December 2019. The researchers showed that these cases were concentrated around the Wuhan market, unlike those recorded in the following months, which coincided with the high-density neighborhoods, indicating the spread of the virus.
Moreover, among the cases studied, people not directly linked to the market lived closer to it than those who worked there or who had recently visited it. This indicates that they were probably infected due to their proximity to this place.
Researchers also analyzed samples taken from the market in January 2020, for example from a cage or carts.< /p>
Their analyzes show that samples positive for SARS-CoV -2 were concentrated in the southwest of the market, precisely where live animals were sold (including raccoon dogs, a species of badger, foxes…).
The animal that acted as an intermediary between the bats, carriers of coronavirus, and the human has not been determined.
Preventing further pandemics
The second study is based on the analysis of the genome of the virus that infected these very first cases. It concludes that two lineages of the virus, A and B, existed before February 2020 and that these two lineages likely resulted from two separate human transmission events, both at the Wuhan market.
Previous studies had suggested that lineage B evolved from lineage A.
Scientists stress that it will be important, in the future, to understand where the animals sold on the Wuhan market came from in order to reduce future risks.
If gray areas therefore remain , the researchers argued that the information available on the beginnings of this pandemic was, in fact, very detailed.
“There is this general feeling that there is no information that can tell us anything about the origin of the COVID-19 pandemic,” commented Kristian Andersen. “It's just not true.”
China has regularly been accused of withholding information or failing to cooperate fully with international investigations. But understanding how this pandemic started is crucial to help prevent similar future events and potentially save millions of lives.
“Pandemics don't require blame, but they do claim to be understood,” concluded Kristian Andersen.