After intense pressure and criticism from many scientists, Chinese researchers last week released a trove of new genetic data that may offer fresh clues about the origin of the COVID-19 pandemic. Some scientists say the new evidence gives more credibility to the thesis that SARS-CoV-2 could have jumped into humans from raccoon dogs or other mammals illegally sold at a Wuhan market. Researchers mainly affiliated with the Chinese Center for Disease Control and Prevention collected 923 samples in or near the market in early 2020 and analyzed the genetic sequences in them. In a preprint posted 13 months ago, they said the abundance of human DNA in samples that contained SARS-CoV-2 "highly suggests" that people brought the coronavirus to the market. The preprint did not mention that some samples positive for the virus also contained genetic evidence that mammals susceptible to SARS-CoV-2 were present. Last week, the team updated the preprint to acknowledge the genetic evidence of the mammals. But the revised manuscript says the samples don't resolve whether infected animals, humans, or even contaminated food introduced the virus to the market, where the first cluster of COVID-19 cases surfaced in December 2019. Chinese authorities shuttered the market on 1 January 2020.
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