The study listed several potential outbreak scenarios by order of likelihood. At the top of the list was animal transmission to humans.
Bats are known to carry a virus closely related to SARS-CoV-2. However, "the evolutionary distance between these bat viruses and SARS-CoV-2 is estimated to be several decades, suggesting a missing link.''
No animal was specified as the missing link. But viruses similar to SARS-CoV-2 have been found in pangolins. Mink and cats are susceptible to the virus, suggesting they could be carriers.
"No firm conclusion" has been made about the role of a Wuhan seafood market in the origin of the outbreak, or how the virus was introduced to the market. The first COVID clusters in Wuhan were traced to the market.
"Cold-chain" transport of frozen food can be a factor in long-distance virus spread, but it was not a major contributor to the outbreak. As the virus spread globally last year, China had reported samples of the virus found on of packaging of frozen food.
Where does the report come from?
The findings are the product of a WHO-led international expert mission carried out from January to February 2021 in Wuhan, the city in central China where COVID-19 was first detected.
The Wuhan Institute of Virology has been the focus of conspiracy theories that claim the virus somehow leaked from the lab and spread around the city.