New studies in ‘Science’ reinforce Wuhan market as origin of first Covid-19 case | coronavirus

Two studies published this Tuesday (26) in the journal “Science”, one of the most important in the world, reinforce the hypothesis that the animal market in Wuhan, in Chinawas where Sars-CoV-2 first spread from animals to humans in the pandemic.

See the main points:

  • One of the surveys mapped transmission patterns in the places where the first Covid-19 cases were detected – and pointed to clusters of cases centered within the Wuhan market.
  • The other concluded that the first two identified strains of the coronavirus were geographically linked to the market — and likely spread from animals to humans on two separate occasions.
  • Neither of the two surveys was done in the Wuhan lab. – but both go against the grain and make “unlikely”, according to scientists, another hypothesis, raised since the beginning of the pandemic, that the coronavirus had been manufactured or leaked from the laboratory. In June, a report by the World Health Organization (WHO) on the source of the disease was inconclusive.

“Do we disprove the lab leak theory? No, we do not refute. But I think what’s really important here is that there are possible and plausible scenarios and it’s really important to understand that possible doesn’t mean equally likely.”

“I myself was pretty convinced about the lab leak until we dived into it very carefully and looked much more closely,” he added.

The first study, of which Andersen is a senior author, incorporated data collected by Chinese scientists to estimate the location of more than 150 of the first Covid cases reported in December 2019.

They also mapped cases from January and February 2020 using data from a social networking app that created a channel for people with Covid-19 to get help.

Scientists have found clusters of cases within the market from Wuhan. These groupings, they said, were “very specific” to the parts of the market where wild animals such as raccoon dogs, susceptible to coronavirus infection, are now known to be sold.

Image shows two raccoon dogs (‘Nyctereutes procyonoides’), susceptible to coronavirus infection. — Photo: Wikimedia

Biologist Michael Worobey, the study’s first author, explained that scientists wondered where the first infected people lived.

“When we were able to look at this, there was an extraordinary pattern where the highest density of cases was extremely close and very centered on that market,” said Worobey, who is at the University of Arizona.

Image shows mapping of the first cases of Covid-19 made by scientists authors of a research published in ‘Science’; study points to the Wuhan market as the origin of the first case of Covid-19. — Photo: Reproduction/Science

Worobey explained that the pattern seen indicates that the virus began to spread among people working in the market – and later, in the local community.

“Crucially, this applies to all cases in December and also to cases with no known link to the market. And this is an indication that the virus started to spread in people who worked in the market, but then it started to spread in the local community.”

Image shows mapping of the first cases of Covid-19 made by scientists authors of a research published in ‘Science’; study points to the Wuhan market as the origin of the first case of Covid-19. — Photo: Reproduction/Science

For Kristian Andersen, who is professor of Immunology and Microbiology at Scripps Research, a research institute in California, “all this evidence tells us the same thing: it points directly to this specific market in the middle of Wuhan.”

already the A second survey – carried out by a separate team of scientists, but also involving Andersen and Worobey – looked at the diversity of the genetic code of the virus inside and outside China.

  • Difficulty ejaculating and reduced libido are among the most common symptoms of ‘Long Covid’

The researchers analyzed the first genomes of samples collected in December 2019 and extended to mid-February 2020. They found that two lineages – A and B – marked the beginning of the pandemic in Wuhan.

The study’s senior author, Joel Wertheim, pointed out that strain A was more genetically similar to bat coronaviruses, but strain B appears to have started to spread earlier in humans, particularly in the marketplace.

That means to say that the virus likely passed from animals to people on two separate occasions.

“I now realize that it looks like I just said that a single event in a generation happened twice in a short succession,” said Wertheim, who is an expert in viral evolution at the University of California at San Diego (UCSD).

But certain conditions were conducive to this – such as people and animals in close proximity and a virus capable of spreading from animals to people and from person to person.

Therefore, the researcher explained, “the barriers to overflow [tradução literal de “spillover”, a transmissão de patógenos de animais selvagens para humanos] were reduced in such a way that, we believe, several introductions [na espécie humana] should be expected”.

For researcher Matthew Aliota, who did not participate in either research, both point to a natural origin of the coronavirus.

“Both studies really provide compelling evidence for the natural origin hypothesis,” said Aliota, who works at the University of Minnesota College of Veterinary Medicine.

Since it’s not possible to sample an animal that was being sold at the market, “this is perhaps as close to a smoking gun as you could get.”

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