Animal Contagion Most Likely Explanation For Covid Genesis, Says Study Animal Contagion Most Likely Explanation For Covid Genesis, Says Study Wuhan is the largest city in central China with multiple animal markets and is a major hub for travel and commerce, well connected to other areas both within China and internationally, the authors said. Wuhan is the largest city in central China with multiple animal markets. Early Covid-19 cases traced to markets in Wuhan, China, mirror the initial spread of SARS 17 years earlier, scientists said in a paper that concludes that an animal contagion is the most likely explanation for the pandemic's genesis.