New studies published in the peer-reviewed journal Science are offering new evidence that the Huanan food market in Wuhan, China, served as the "early epicentre" of the COVID-19 pandemic.
A statement from the (AAAS), which publishes the journal Science, says the scientists who authored the studies concluded that SARS-CoV-2, the coronavirus that causes COVID-19, was likely present in live mammals sold at the Huanan Seafood Wholesale Market in late 2019 before infecting people.
They say future studies should focus on where the wild mammals sold at Huanan came from, which could help prevent the risk of future pandemics.
"Despite the observation that the preponderance of earliest known COVID-19 cases – flagged by hospitals in Wuhan in December 2019 – were linked to the Huanan market, this did not establish activities at the Huanan market as the trigger for the pandemic," the AAAS statement says.
The studies come after an expert group drafted by the World Health Organization said in June that more research is needed to determine how COVID-19 first began, including the possibility of a laboratory accident.
Preprint, or non-peer reviewed, versions of the studies were released in February.
In one of them, to estimate the longitudes and latitudes of more than 150 of the earliest reported cases from December 2019, including those without any notable direct links to the market.
They say the highest density of cases centred around the market in Wuhan.
The researchers also mapped cases from January and February 2020 using a channel on the Chinese social media app Weibo that was created for people who had COVID-19 and sought medical help.
Using this data, they found cases in other parts of central Wuhan stemming from the market.
They say live mammals susceptible to SARS-CoV-2, including red foxes, hog badgers and common raccoon dogs, also were sold live at the market in late 2019.
The researchers note that while they were able to recover location data for most December 2019 COVID-19 cases, the exact longitudes and latitudes were not available for all of them.
There is also no direct evidence of an intermediate animal becoming infected with early SARS-CoV-2 at either the Huanan market or another location in its supply chain, such as a farm, they say.
In the second study, researchers looked at the genetic diversity of early SARS-CoV-2, .
The scientists say only lineage B was found in 11 sequenced genomes from people who were directly associated with the Huanan market.
People with lineage A genomes, meanwhile, had no known contact with the market but did live or stay nearby.
The scientists believe both lineages were circulating in non-human mammals, with lineage B first appearing in humans likely in mid-November 2019, followed by lineage A within days or weeks.
Similar to the previous study, the researchers say they lack direct evidence of a virus, closely related to SARS-CoV-2, present in non-human mammals at the market or its supply chain.
