Covid 19 started with live animals sold in the Wuhan, China market at the end of 2019. This is the conclusion reached by the authors of the studies published in 2 articles in the journal Science. The analysis coordinated by Professor Michael Worobey – director of the Department of Ecology and Biology at the University of Arizona – involved experts of different nationalities and produced the texts that effectively exclude any alternative hypothesis for the origin of the pandemic. According to the authors, the passage of the virus from animals to humans occurred in two distinct events, in the Huanan market – in Wuhan – at the end of 2019.
One of the studies looked at the location of the earliest known cases of Covid 19, combining the information with the results of analyzes on swabs taken from surfaces and cages in various sections of the market. The other study focused on SARS-CoV-2 genomic sequences after analyzing samples provided by patients who tested positive during the first weeks of the pandemic in China.
The first study, conducted by Worobey and Kristian Andersen at the Scripps Research Institute in San Diego, California, looked at the geographic pattern of Covid 19 cases in the first month of the outbreak, December 2019. The scientists were able to determine the location of almost all 174 cases of Covid 19 identified by the World Health Organization in the month in question.
The analyzes showed that the cases were concentrated around the Huanan market, while subsequent infections have spread widely in the city of Wuhan, inhabited by 11 million people. In particular, the researchers found that a surprising percentage of the first Covid patients with no direct link to the market – they were not workers or customers – were still located in the areas adjacent to the commercial facility.
“This reinforces the idea that the market was the epicenter of the epidemic,” says Worobey, explaining that vendors and workers were infected first and actually started a chain of infections.
“In a city that covers more than 5,000 square kilometers, the area most likely to house the home of someone among the first infected in the world was in a perimeter of a few streets, with the Huanan market right inside it. “explains Worobey.
Scientists also examined samples taken from market surfaces, such as floors and cages, after the facility was closed. Samples that tested positive for SARS-CoV-2 were associated with stalls selling live wild animals.
The researchers determined that the mammals now known to be susceptible to the infection – red foxes, badgers and raccoons – were being sold alive at the Huanan market in the weeks before the first human cases were registered.
“Upstream events remain obscure, but our analysis of the available evidence suggests the pandemic stemmed from human infections from animals sold at the Huanan Seafood Wholesale Market at the end of November 2019,” the summary. by Andersen, co-lead author of both studies.
The second study, a genetic analysis from early cases, was co-directed by Jonathan Pekar and Joel Wertheim of the University of California, San Diego, and Marc Suchard of the University of California, Los Angeles.
Scientists determined that the pandemic, which initially involved two slightly different SARS-CoV-2 lineages, likely resulted from at least two human animal-induced infections in the Huanan market in November 2019 and possibly December 2019. The most likely hypothesis is that the two lineages were transferred from animals to humans in two distinct episodes.