Two new studies published in Science point back to wuhan chinese market as the epicenter of the emergence of SARS-CoV-2 due to activities associated with the wildlife trade.
The investigations, led by michael worobey s Jonathan Pékaruse complementary approaches involving spatial and environmental analysislike this molecular studiesto provide evidence that the pandemic originated in this space.
The experts conclude that it is very likely that SARS-CoV-2 was present in live mammals that were sold in the city in late 2019 and also suggest that the genomic diversity of the virus before February 2020 likely comprised only two viral strainsdesignated A and B. These lineages were the result of at least two separate events of interspecies-to-human transmission.
The infection center and the sale of wild animals
To test the hypothesis that the market was the epicenter of the pandemic, Worobey and his team at the University of Arizona used cartographic tools estimate the location in longitude and latitude of more than 150 of the first cases reported in December 2019, including those not directly linked to the market. The highest density of these cases was concentrated around that space.
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By mapping the January and February 2020 cases using data from Weibo, a social media app which created a channel for people with covid to seek medical help, researchers identified cases in other parts of central Wuhan radiating from the market as the pandemic progressed.
On further analysis, the scientists noted that several potential wildlife carriers were being sold there until at least November 2019. Specifically, they identified five stalls likely selling live or freshly slaughtered mammals; according to the analyses. Subsequently, the owners of these tents were infected with the virus.
Two SARS-CoV-2 strains, designated A and B, marked the beginning of the pandemic in Wuhan. / Pixabay
A virus with two separate strains
For its part, to better understand the circumstances that led to the origin of the pandemic, Beijing and his group at the University of California at San Diego analyzed the genomic diversity of SARS-CoV-2 at the beginning of the pandemic. While this has increased as the pandemic has spread from China to other countries, two strains of SARS-CoV-2, designated A and B, marked its beginnings in Wuhan.
The scientists used genomic and epidemiological data of the first moments of the pandemic with models and simulations to test their hypotheses. The conclusion is that the first zoonotic transmission likely involved lineage B viruses around November 2019, while the separate introduction of lineage A likely occurred days or weeks after this event.
As with other coronaviruses, the appearance of SARS-CoV-2 was likely the result of various events zoonotic.
Worobey’s results are also consistent with this idea of a separate origin and the subsequent appearance of strain A on the market in late November 2019.
These findings indicate that the virus is unlikely to have circulated widely in humans before November 2019, and describe the narrow window of time between when SARS-CoV-2 first jumped to humans and when the first cases were reported.
