Two studies, published online July 26, 2022 in the journal Science, report that the Huanan Live Animal Market in Wuhan, China was the epicenter of the emergence of the Covid-19 pandemic and that it has been manifested by the transmission from animals to humans of at least two distinct viral lineages.
As we know, it all started on December 31, 2019, when the Chinese government notified the World Health Organization (WHO) of the appearance of an epidemic of severe pneumonia of unknown cause in Wuhan (Hubei province), city with about 11 million inhabitants. On January 2, 2020, 41 people were hospitalized with a mysterious pneumonia. Among them, 27 had had direct contact with the Huanan market in the city of Wuhan where live animals were sold. The first diagnoses of what will be called Covid-19 were made in several hospitals between December 18 and 29, 2019.
A systematic review published in a report by the WHO-China joint mission had shown that 55 of the first 168 cases of Covid-19 were associated with the Huanan Seafood Wholesale Market.
“Our results show that Huanan Market was the early epicenter of the Covid-19 pandemic and suggest that SARS-CoV-2 likely emerged through the live wild animal trade in China,” says Michael Worobey , Andrew Rambaut, Kristian Andersen and their colleagues.
It turns out that the first cases of Covid-19 were in people living near or around Huanan Market. Although lacking the precise coordinates of the homes of 164 patients living in Wuhan, the researchers were able to determine the latitude and longitude of 155 cases from maps in the WHO-China joint mission report.
The clustering of Covid-19 cases in December 2019 around the Wuhan market contrasts with what was observed between early January and mid-February 2020 when the spread of cases was more dispersed in Wuhan. These cases that appeared secondarily were traced via location data from an assistance application for people with Covid-19 produced by the social network Sina Weibo.
Diagram showing the location of SARS-CoV-2 positive environmental swabs and human cases in the western market area of Wuhan. The rectangular area surrounded by a hatched line delimits the "wildlife" area of the market. The photo on the left (taken by Edward Holmes of the University of Sydney in 2014) shows the stacking of cages in which raccoon dogs and live birds are kept. Worobey M, et al. Science. 2022 Jul 26:abp8715.Many animal hosts may have harbored the ancestor viruses of SARS-CoV-2, including red foxes, hog badgers and raccoon dogs. This carnivorous mammal, predator of bats and which resembles a raccoon, often hides in places where bats are found. Raccoon dogs are sold year-round for both meat and fur. It is known that these animals were sold at least until November 2019. It is recalled that it is still unknown what is the intermediate animal host infected with SARS-CoV-2 which would have been present on the Huanan market or on a farm. supplying the merchants of this place of sale of live animals.
Five environmental swabs collected from a single location selling live animals in late 2019 were found to be positive for SARS-CoV-2. In addition, the objects sampled included a metal cage, two carts (of the same type frequently used to transport animal cages), and an instrument for shearing or removing feathers.
Edward Holmes, one of the authors of the article, a researcher at the University of Sydney, had the opportunity, in 2014, to observe raccoon dogs locked in a metal cage arranged above a cage containing live birds. A recent report indicated that the wire mesh around this stall, on which the cages of these animals were stacked, had tested positive for SARS-CoV-2. It had also been shown that the virus was also present in the water evacuating from this location and a neighboring location...
the pandemic most likely began with at least two separate crossings of the species barrier from animals to humans in November 2019.
The authors are formal: their epidemiological simulations are not compatible with the hypothesis of a single introduction of SARS-CoV-2 in humans to explain the genetic diversity of this virus, what is called its phylogeny. Conversely, their models strongly favor separate introductions of A and B lineages.