Researchers analyzed genetic material gathered from the Chinese market where the first outbreak was detected and found that the most likely animals were racoon dogs, civet cats and bamboo rats. The scientists suspect infected animals were first brought to the Wuhan market in late November 2019, which then triggered the pandemic.

Michael Worobey, one of the new study's authors, said they found which sub-populations of animals might have transmitted the coronavirus to humans. That may help researchers pinpoint where the virus commonly circulates in animals, known as its natural reservoir.

"For example, with the racoon dogs, we can show that the racoon dogs that were (at the market) … were from a sub-species that circulates more in southern parts of China," said Worobey, an evolutionary biologist at the University of Arizona. Knowing that might help researchers understand where those animals came from and where they were sold. Scientists might then start sampling bats in the area, which are known to be the natural reservoirs of related coronaviruses like SARS.

While the research bolsters the case that COVID-19 emerged from animals, it does not resolve the polarized and political debate over whether the virus instead emerged from a research lab in China.