The White House published a post on its official website on the 18th of last month, stating that the virus causing COVID-19 leaked from the Wuhan Institute of Virology in China. As the theories of natural occurrence and laboratory leak of the COVID-19 virus are contending in the United States, research results directly countering the White House's claims were published in an international academic journal. The assertion is that the virus leaked through the transaction of wild animals.
A team of researchers from the University of California, San Diego (UC San Diego) School of Medicine noted on the 8th that the ancestor of the COVID-19 virus first emerged in western China or northern Laos and then moved to Wuhan, China, thousands of kilometers away through wildlife transactions.
The UC San Diego researchers traced the evolutionary pathway of the virus by analyzing the genetic information of the Sarbecovirus group, which caused the severe acute respiratory syndrome (SARS) in 2002 and the COVID-19 pandemic.
Joel Wertheim, a professor at UC San Diego, explained, "Sarbecovirus primarily uses bats as hosts, and because there are often genetic combinations among various viruses within bats, it was challenging to clarify the evolutionary pathway. This time, we focused on analyzing specific regions where no genetic recombination occurred to reveal the evolutionary history."
The analysis confirmed that the virus that triggered the SARS pandemic (SARS-CoV-1) and the COVID-19 virus (SARS-CoV-2) spread throughout western China and Southeast Asia over thousands of years. During this period, the transmission rate of the virus was similar to the movement speed of its host, bats.
However, before causing a pandemic, SARS-CoV-1 moved from western China to Guangdong Province within 1 to 2 years, while SARS-CoV-2 appeared to have traveled from western China or northern Laos to Wuhan within 5 to 7 years. This indicates that it moved over a distance of 1,000 kilometers in a matter of years.
The researchers stated, "Considering that the primary hosts, bats, forage and move within an average radius of 2 to 3 square kilometers, the likelihood of the virus being transferred solely through bat movement is very low. It is much more likely that the virus was transferred to an intermediate host animal through wildlife transactions and subsequently transmitted to humans."
Previous studies suggested that SARS-CoV-1 might have been transmitted from Yangtze River civets and raccoons, commonly traded wildlife, from Yunnan Province in China to Guangdong Province. This study indicates that the COVID-19 virus may have been transmitted to humans in a similar manner.
Professor Wertheim explained, "The results of this study raise questions about the hypothesis that the COVID-19 virus originated from a laboratory leak due to the considerable distance between Wuhan and the bat virus reservoir. It seems to have spread along wildlife transaction routes, separate from the laboratory leak theory."
The researchers commented, "Wildlife transactions and human encroachment into nature are causing these 'inter-species transmission' events," noting, "By continuously tracking Sarbecoviruses in wild bat populations, it might be possible to uncover the cause of the next pandemic."
References
Cell (2025), DOI: https://doi.org/10.1016/j.cell.2025.03.035