New studies show that SARS CoV2 emerged from live animal market in China’s Wuhan

New studies released over last week have pointed out that SARS CoV2 or Coronavirus likely emerged from a large food and live animal market in Wuhan, China. After analysing a wide range of data, including virus genes, and social media activity of early Covid-19 patients across Wuhan, scientists have concluded that coronavirus was very likely present in live mammals sold at the Huanan Seafood Wholesale Market in late 2019.

The New York Times reported, the studies have suggested that the virus entered into people working or shopping there on two separate occasions. It was earlier suspected that the outbreak began with a leak from a Wuhan virology lab. An evolutionary biologist at the University of Arizona and a co-author of both new studies, Michael Worobey, underscored that if all the evidence is put together, it becomes evident that the pandemic started at the Huanan market.

Both the studies debated the beginnings of the pandemic which has killed more than 60 lakh people across the world. According to official statistics, there have been 5.14 lakh deaths in India, but RTI responses have shown that uncounted Covid-19 deaths across the country could amount to almost double this figure.

Though both the the pre-print studies have showcased compelling and rigorous new analysis of available data, several scientists pointed to gaps that still remained in the studies. The new papers did not, for example, identify an animal at the market that spread the virus to humans.

According to NYT, scientists at the Chinese Center for Disease Control and Prevention published another study where they had analysed genetic traces of the earliest environmental samples collected at the market, in January 2020.

By the time Chinese researchers arrived to collect these samples, police had shut down and disinfected the market because a number of people linked to it had become sick with what would later be recognised as Covid. No live market animals were left.

The researchers swabbed walls, floors and other surfaces inside the market, as well as meat still in freezers and refrigerators. They caught mice, stray cats and dogs around the market to test them, while also testing the contents of the sewers outside. The researchers then analysed the samples for genetic traces of coronaviruses that may have been shed by people or animals.

Although the Chinese researchers conducted their study over two years ago, it was not until last week that they had publicly shared the results. They concluded that the Huanan market samples included two evolutionary branches of the virus, known as lineages A and B, both of which had been circulating in early Covid cases in China.

The results came as a surprise because earlier the only Covid cases linked to the market appeared to be Lineage B. And because Lineage B seemed to have evolved after Lineage A, some researchers suggested that the virus arrived at the market only after spreading around Wuhan.

Although the Huanan market was an early object of suspicion, by the spring of 2020, senior members of the Donald Trump administration were promoting the idea that the new coronavirus had been leaked from the Wuhan Institute of Virology, a coronavirus laboratory located eight miles away on the other side of the Yangtze River. The researchers there have denied that Coronavirus spread due to a leak from the lab.

In January 2021, experts chosen by the World Health Organisation had travelled to China and they released a report in March 2021 that contained previously undisclosed details about the market. They noted, for example, that 10 stalls in the southwest corner of the market sold live animals. The report also noted that 69 environmental samples collected from the market by the Chinese officials had turned up positive for SARS-CoV-2. But the frozen meat and live animals had all tested negative.

The WHO experts had also identified 164 cases of Covid-19 in Wuhan over the course of December 2019. Worobey and his colleagues used mapping tools to estimate the locations of 156 of those cases and it was revealed that the highest density of December cases was centered around the market. The researchers reconstructed the floor plan and they found that several cases were clustered around where the live animals were sold.