TUCKER BEGS TO DIFFER:

The first cluster of coronavirus cases in humans was linked to the Huanan Seafood Wholesale Market in Wuhan, China (SN: 1/24/20). Environmental samples taken in 2020 from the southwest corner of the market, where live animals were sold, carried genetic material from both the coronavirus and animals, the Atlantic first reported on March 16.

In some virus-positive samples, computational biologist Alex Crits-Christoph and an international team of colleagues also found DNA from the common raccoon dog (Nyctereutes procyonoides). The foxlike animal native to Asia is susceptible to coronavirus infections, including SARS-CoV-2, the virus that causes COVID-19.  

The fact that traces of both animal and coronavirus were uncovered in the same samples suggest that the virus may have jumped from bats to raccoon dogs or other animals at the market and then to people, the team writes (SN: 7/12/21). It posted its analysis March 20 on Zenodo, a repository where scientists can post research results that have not yet been reviewed by their peers.

This analysis builds on evidence from two studies published in Science in July 2022. In the first study, researchers reported that the genetic diversity of SARS-CoV-2 variants from the pandemic's early days suggest that there may have been two separate jumps from animals to people: one in late November 2019 and another weeks later. The second study used the first known COVID-19 cases and coronavirus-positive environmental samples from the seafood market to identify the southwest part of the market with live animal vendors as the likely epicenter of the pandemic's spread.

In the new analysis, Crits-Christoph, who works from Baltimore for the nonprofit Cultivarium, and colleagues analyzed public genetic data that had been released in early March from the Chinese Center for Disease Control and Prevention. That data, linked to a February 2022 preliminary study from the China CDC (which is now under review at a scientific journal), allowed the team to zoom in on an animal stall in the southwest part of the market that had the most virus-positive samples. A sample from a cart in that stall also contained plenty of genetic material from raccoon dogs, as well as a handful of other animals such as ducks.

There was no evidence of human DNA in that sample, a finding that hints that animals, not necessarily people, were close to the coronavirus in that spot. Raccoon dogs or another animal, the results suggest, might have served as a bridge to take the coronavirus from bats to humans.

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