An international team of researchers has concluded that live animals sold at a wholesale Huangan seafood market in China were the likely source of the COVID-19 pandemic. Led by University of Arizona virus evolution expert Michael Worobey, the researchers traced the beginning of the pandemic to a market in Wuhan, where foxes, raccoon dogs and other live mammals susceptible to the virus were sold just before the pandemic began. Their findings were published in the journal Science. The first paper, led by Worobey and Kristian Andersen of the Scripps Research Institute in San Diego, California, examined the geographic pattern of COVID-19 cases in the first month of the outbreak, December 2019.  The analysis showed that the cases were clustered closely around Huangan Market, while later cases were widely dispersed throughout Wuhan, a city of 11 million people.  The researchers found that mammals now known to be susceptible to SARS-CoV-2, including red foxes, hog badgers and raccoon dogs, were sold alive at Huangan Market in the weeks leading up to the first reported COVID-19 cases.  The second study, an analysis of SARS-CoV-2 genomic data from the early stages of the disease, was led by Jonathan Pekar and Joel Wertheim of the University of California, San Diego, Marc Suchard of the University of California, Los Angeles, and Andersen and Worobey.  The authors used a method known as molecular clock analysis, which relies on the natural rate at which genetic mutations occur over time, to provide a framework for the evolution of SARS-CoV-2 virus lines. Previous studies have suggested that one lineage of the virus, named A and closely related to related bat viruses, gave rise to a second lineage, named B. According to the new data, a more likely scenario is that the two lines passed from animals to humans in separate cases, both in the Huangan market, Worobey said.