Covid: new studies again point to the Wuhan market as the epicenter of the disease

Scientists say there is “compelling evidence” that the Huanan Seafood and Wildlife Market in the Chinese city of Wuhan was the epicenter of the Covid-19 outbreak.

Two peer-reviewed studies published Tuesday (7/26) re-examine information from the initial outbreak in the Chinese city.

One of the studies shows that the first known cases appeared in and around the market. The other uses genetic information to understand the chronology of the outbreak.

This suggests that there were two variants introduced to humans in November or early December 2019.

The researchers say there is evidence that Sars-Cov-2 was present in live mammals that were sold at the Huanan market in late 2019. Scientists say the coronavirus was transmitted to people who were working or shopping there in two” separate “overflow infections” – in which a human has contracted the virus from an animal.

One of the researchers involved, virologist David Robertson from the University of Glasgow in Scotland, told BBC News that he hopes the studies “correct the false history that the virus came from a laboratory”.

Epicenter of the pandemic

Two years of scientific effort to understand the virus that causes Covid-19 have given scientists a new perspective.

This allowed them to understand an important conundrum about early patients: of the hundreds of people hospitalized with covid-19 in Wuhan, only about 50 had a direct, traceable link to the market.

“It was really intriguing that most of the cases were not linked to the market,” says Professor Robertson. “But knowing what we now know about the virus, that’s exactly what we expected: because a lot of people get only mildly sick, so they’re in the community passing the virus on to other people but it’s difficult to connect severe cases to them.”

This Covid-19 case mapping survey revealed that a large percentage of early patients with no known connection to the market – meaning they did not work or shop there – lived near it.

This supports the idea that the market was the epicenter of the epidemic, says Professor Michael Worobey, lead author of the study and a biologist at the University of Arizona, in the United States.

According to him, sellers were the first infected and set off a “chain of infections among community members in the surrounding area”.

The scientist says that in a city with more than 7,770 square kilometers, the houses closest to the market were more likely to register the first cases of covid-19.

This study also focused on the market itself. Scientists created a map with fluid samples from drains and market stalls, which had tested positive for the virus.

“Most of the positive samples came from the southwest side of the market,” explains Robertson. “And this is where species like raccoon dogs were being sold. So we have confirmation that animals that we now know are susceptible [ao Sars-Cov-2, o vírus que causa o covid-19] were sold there at the end of 2019”.

The lab leak theory

Over the past two years, the search for the source of the deadly pandemic has shifted from a scientific investigation to a toxic political dispute.

One of the most violent international controversies – particularly among politicians in the US and China – was a theory that the virus could have leaked from a laboratory at the Wuhan Institute of Virology.

But that hypothesis, says Professor Stuart Neil of Kings College, “does not explain the data.”

“We are now as certain as we can be, based on the fragmentary evidence we have, that this was a spillover infection that happened in the market.”

Many scientists agree that markets teeming with live animals create an ideal environment for new animal diseases to spill over into humans. And in the 18 months until the start of the pandemic, a separate study showed that nearly 50,000 animals from 38 different species were sold in markets in Wuhan.

Neil said the pandemic was likely a consequence of an “unhealthy, cruel and unhygienic practice that the Chinese authorities had been warned about”.

For him, the biggest problem with trying to blame a lab for all this “is that we run the risk of letting it happen again by focusing on the wrong problem.”