The source of the COVID-19 pandemic has been identified

A new study conducted by scientists from the United States (US) and France, using millions of genetic code fragments, suggests that the COVID-19 pandemic emerged from infected animals sold at a market rather than a laboratory leak.

The study utilized samples collected by Chinese authorities during the early stages of Covid, which are considered one of the most valuable sources of scientific information regarding the origins of the pandemic.

The samples were collected in the city of Wuhan, China, in January 2020.

An early link to the Huanan Seafood Wholesale Market had been established as the number of people presenting to hospitals in Wuhan with a mysterious pneumonia increased.

After the market was closed, authorities collected swab samples from many places, including stalls, the insides of animal cages, and equipment used to skin slaughtered animals.

Analyses regarding these samples were published last year, and the raw data were made available to other scientists.

VIRUSES REVIVED

Now, a group of scientists in the USA and France say that more advanced genetic analyses have allowed them to delve deeper into the early days of Covid.

As part of this study, they had to analyze millions of short genetic code fragments (both DNA and RNA) to effectively reconstruct the animals and viruses that were present in the market in January 2020.

Prof. Florence Débarre of the French National Centre for Scientific Research says, "We see the DNA and RNA ghosts of these animals in environmental samples, and some of these animals are at the stalls where [the Covid virus] was found."

The research results published in the journal Cell list findings that support the thesis that the virus emerged at the market.

Accordingly, it was determined that the Covid virus and animals susceptible to carrying it were in the same location; in some swabs, both the animal's and the coronavirus's genetic code were observed together. These were not distributed evenly throughout the market; they were concentrated in specific hotspots.

Prof. Kristian Andersen of the Scripps Research Institute in the US says, "Even at the level of a single stall, we find a very consistent story that points to the market as the highly probable source of the outbreak."

However, the fact that they were in the same place at the same time as the virus does not prove that the animals were infected.

The most common animal found in the samples was the raccoon dog. Experiments had shown that this animal both contracted and transmitted Covid.

Other animals identified as potential sources of the pandemic were the masked palm civet, which was also linked to the 2003 SARS outbreak, bamboo rats, and Malayan porcupines. No experiments were conducted to see if they spread the virus.

The depth of the genetic analysis made it possible to determine which species of raccoon dogs were being sold in the market. These species were more commonly found in the wild in Southern China. This provides scientists with clues as to where to look next.

"THE SOURCE IS ANIMALS, BEYOND ANY DOUBT"

The research team also compared the genetic code of viral samples found at the market with samples taken from patients in the early days of the pandemic. Examining various mutations in the viral samples also provided clues.

The samples show, but do not prove, that Covid emerged in the market multiple times and that there were two potential spillover events from animals to humans.

Researchers say this supports the idea that the market was the origin, rather than the outbreak starting somewhere else and gaining strength at the market.

Scientists also used the mutations to build the virus's family tree and look into its history.

Prof. Andersen says, "The times when we believe the pandemic and the outbreak at the market began overlap; they are the same."

According to their research, the entire genetic diversity of the coronavirus seen in the early days of the pandemic was present at the market.

Prof. Michael Worobey from the University of Arizona says, "Rather than being a small branch on this large, bushy evolutionary tree, the genetic sequences at the market are spread across all branches of the tree, which is consistent with the genetic diversity actually starting at the market."

He stated that when this study is combined with other data, such as early cases and hospitalizations linked to the market, it points to an animal origin for Covid.