Two studies published this Tuesday have concluded that the Covid-19 pandemic began in a market in the Chinese city of Wuhan, pointing to animal origin as a possible cause of the virus.
The first study was a geographic analysis, which showed that the first cases detected in December 2019 were concentrated in that market.
The second investigation was a genetic analysis of the virus from the first cases, which showed that the virus was unlikely to have spread widely among humans before November 2019.
The studies were published this Tuesday in the journal Science, reports Agence France-Presse (AFP).
Since the start of the Covid-19 pandemic, there has been an ongoing debate among experts, which continues almost three years later to clarify the mystery of the origin of the SARS-CoV-2 virus.
One of the authors of these studies, virologist Michael Worobe of the University of Arizona, signed a letter in 2021 calling for serious consideration of the possibility of a leak from a laboratory in Wuhan.
However, with the data analyzed since then, the scientist now “does not believe that the virus was introduced by the animal trade in the market in Wuhan,” he explained at a press conference.
Christian Andersen of the Scripps Research Institute, a co-author of the studies, stressed that while the lab escape theory has not been disproved, it is important to “understand the possible scenarios and what is possible.”
The first study looked at the residences of the first 155 cases identified in December 2019.
The researchers showed that these cases were concentrated around the Wuhan market, which, unlike those recorded in subsequent months, coincided with more densely populated neighborhoods.
Additionally, in the cases studied, individuals not directly connected to the market lived closer than those who had recently worked or visited.
This indicates that they are probably infected due to their proximity to the site.
The scientists analyzed samples taken from the market in January 2020, for example from cages or carts.
Positive samples for Sars-Cov-2 were concentrated in the southwest of the market, precisely where live animals were sold (including raccoon dogs, a type of badger or foxes).
The animal that acted as an intermediary between bats, the carriers of the coronavirus, and humans has not been identified.
The second study was based on an analysis of the genome of the virus that infected the first people.
The analysis concludes that two strains of the virus, A and B, existed prior to February 2020 and that these two strains may have resulted from two separate human transmission events in the Wuhan market.
Previous studies suggest that the lineage evolved from A.
To reduce future risks, it is important to understand where the animals sold in the Wuhan market came from, scientists warn.
Although ‘grey areas’ remain, the researchers underline that information about the beginning of the epidemic is very comprehensive.
“There is a general feeling that we don’t have any information that can tell us anything about the origins of the COVID-19 pandemic. This is wrong”, underlined Christian Andersen.
China is constantly accused of failing to cooperate fully with international investigations or of concealing information.
Understanding how the pandemic started can help prevent future events like this and save millions of lives.
“Infectious diseases do not need to name a responsible person, but they need to be understood,” concluded Christian Andersen.