August 18, 2022

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Wuhan market in the origins of Covid-19: how the virus was born and how to avoid other epidemics

Science has published two works that help understand more about the spread of the SARS-CoV-2 virus, from the wet market in the Chinese capital to the entire world, between leaps and developments of species. Limit contact with some animals to prevent a re-emergence of the disease

The July 26 issue of Science contains two works, which appeared in their first print edition in February, that shed some light on theThe origin of the SARS-CoV-2 pandemic.

In the first jobThe researchers analyzed the geographic distribution of documented cases in the first month for which data is available, specifically December 2019. In a city like Wuhan, with an area of ​​more than 7,700 square kilometers, the area with the highest probability of containing home from some of the world’s first documented cases of COVID-19 covers a few Blocks, with Huanan Market right in the middle.

The researchers were able to pinpoint the area frequented by 155 of the 174 COVID-19 cases identified by the World Health Organization in December 2019. These cases appear to be clustered closely around the Huanan market. While subsequent cases are widespread throughout Wuhan, a bustling megacity of 11 million people. Moreover, among the first patients, all those who did not visit the market in the vicinity of disease development, resided more statistically near it than the patients who visited, which proves to be the risk factor between the development of the first known cases of COVID-19 and proximity to market.

In addition, it was possible to determine that some animals known to be infected with SARS-CoV-2, including red foxes, pig-nosed badgers, and raccoon dogs, were sold live at the Huanan market in the weeks before the first cases of COVID were recorded. -19. In a detailed map, samples positive for SARS-CoV-2 reported by Chinese researchers in early 2020 were associated with the western part of the market, where these live or freshly slaughtered animals were sold in late 2019.

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In light of this latest evidence, Huanan Market is emerging not only as the place of the initial amplification of the epidemic, but also the place where the jump of species and the initial evolution that led to the emergence of the first epidemic strain took place. This image is consistent with genomic and epidemiological data from The second study just published.

In this second study, the authors examined the early development of the virus based on the first sampled genome. They found that the epidemic initially included two subtly distinct strains of SARS-CoV-2, which means that its release was likely caused by at least two separate human infections caused by animals in the Huanan market, around the end of November 2019.

Interestingly, the same analyzes also indicate that, in this space and time, there were many different independent animal-to-human infectious events in the market, which nevertheless did not cause an epidemic.; Therefore, the market was for an initial period the scene of a series of evolutionary experiments with coronaviruses, many of which, as expected, were aborted, before at least two succeeded and led to the subsequent catastrophe.

Taken together, the two newly published studies suggest that SARS-CoV-2, as has already happened to other coronaviruses, arose from zoonoses, certainly multiple, in this case from animals sold at a particular market in Wuhan.. Prior to these events, there must be infection of intermediate animal hosts by viruses from bats, perhaps in the areas of origin of meat and live animal sellers, or at least in the areas of their sellers.

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To shed more light, it will therefore be necessary to focus on the initial flow of pandemic emergence, that is, the spread of pre-infectious viruses to the market and their arrival in the market for a longer or less period, before prolonged contact between the Wuhan population and intermediate vectors introduced a sufficient number of indirect opportunities, such as the interception of variables with characteristics suitable for propagation in humans.

Furthermore, this picture of multiple infection by different viral variants was subsequently documented in other instances of spread to humans by SARS-CoV-2: for example, there were at least two zoonotic jumps of SARS-CoV-2 in humans from hamsters. Domestic in Hong Kong and dozens of mink to humans on Dutch fur farms.

In light of this data, Reducing contact with different animal species is an essential goal of epidemic preventionThe more different potential vectors that many humans come into contact with, the greater the risk of developing new and devastating zoonotic diseases. Trade in exotic animals, fur animal husbandry and in general any form of exploitation of wild species should be abandoned, in light of a risk/benefit analysis which clearly indicates the prevalence of the former over the latter from a public health point of view.