A new study confirms the suspicion that the coronavirus pandemic most likely started in a wildlife market in the Chinese metropolis of Wuhan. Accordingly, samples infected with SARS-CoV-2 collected around a market stall selling civet cats and raccoon dogs.
Both species were already carriers of the SARS pandemic in 2002/2003 and are also suspected as intermediate hosts for SARS-CoV-2. At that time, almost 800 people died from more than 8,000 cases worldwide. The main affected areas were China, Taiwan, Vietnam, Singapore and Canada (Toronto).
Severe acute respiratory syndrome (SARS) is an infectious disease caused by the SARS coronavirus (SARS-CoV) and has the clinical picture of atypical pneumonia. The virus is transmitted from person to person, mainly by inhalation of infectious droplets from contact with sick people.
Coronaviruses similar to the SARS virus have now been detected in wild Chinese small mammals – such as raccoon dogs (pictured below) and civet cats – so it can be assumed that the infection mainly originated from such animals.
A new study provides a short list of the wild animal species present in the market from which SARS-CoV-2, the pathogen responsible for the Covid-19 pandemic, most likely emerged in late 2019.
More than 800 samples evaluated
The study, published in the journal Cell, is based on an analysis of genetic data published by China’s Center for Disease Control and Prevention (CDC) from more than 800 samples collected from January 1, 2020, in and around the Huanan Seafood Market in Wuhan, as well as viral genomes from the first Covid-19 patients.
For the study, a team led by Michael Worobey of the University of Arizona analyzed DNA and RNA from animal barns, surfaces, and sewage drains for both the presence of SARS-CoV-2 and the exact genetic lineage of the coronavirus (pictured below).
Unlike previous studies, this time the team also identified more precisely which animals were present at the market stalls that were most heavily infected with the coronavirus. This allowed them to draw up a ‘shortlist’ of potential carrier animals and their origins.
“Last piece of the puzzle in a relatively clear picture”
“We’ve analyzed the data in a new, rigorous way and shown how it fits with the rest of the evidence we already have about the beginning of the pandemic,” Worobey said. “It’s the final piece of the puzzle in an already relatively clear picture,” the scientist said.
Recent analysis of the data showed that SARS-CoV-2 was present in some stalls where wild animals were also sold at the market. These wild animals included raccoon dogs and civet cats. In some cases, genetic material from the coronavirus and these animals was found on the same swabs.
The researchers also conducted an evolutionary analysis of the earliest reported viral genomes. The results suggest that very few, if any, people were infected before the pandemic began. This points to transmission from animals to people at the market and then spread in Wuhan and eventually around the world, Worobey said.
“The spark in a tinderbox”
Bringing virus-infected wild animals into contact with people in the heart of big cities, where population density makes it easy for pathogens to establish themselves, is one of the riskiest things people can do, Worobey said.
“Not all of these viruses have the potential to cause a pandemic, but if you introduce them, it’s like a spark in a tinderbox,” he said.
Source: Krone
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