An international research team that included a UCLA professor of biostatistics concluded in research published Tuesday that the COVID-19 pandemic originated at a wholesale market in Wuhan, China, where at least two instances of the virus being passed from live animals to humans were detected.
“Rigorously combining all available evidence surrounding the emergence of SARS-CoV-2 clearly demonstrates that the virus jumped at least twice from animals to humans at the Huanan market,” Dr. Marc Suchard, UCLA Fielding School professor of biostatistics, said in a statement. “Identifying multiple transmission events finally puts to rest a single origin from elsewhere.”
Identifying the source of the pandemic that has led to more than six million deaths globally has been a politically charged and hotly debated process. But the research team concluded that live animals sold at the Huanan Seafood Wholesale Market were the likely origin point — countering the idea the virus escaped from the nearby Wuhan Institute of Virology.
The research, which has undergone peer review, was published Tuesday, July 26, in the journal Science.
The authors of the study determined that there were two separate instances of transmission of the virus from animals to humans at the market in late 2019.
Researchers studied the locations of the first known COVID-19 cases and reviewed genomic sequences of the virus from patients during the first weeks of the pandemic in China. Studying the locations of almost all 174 COVID- 19 cases identified by the World Health Organization in December 2019 when the outbreak began, 155 were determined to be in Wuhan, and they were tightly clustered around the Huanan market, according to the study. Researchers also noted that of the early COVID-19 patients who neither worked nor shopped at the market, most lived nearby.
“This supports a scenario in which the market was the epicenter of the epidemic,” said researcher Dr. Michael Worobey, a viral evolution expert from the University of Arizona. “With vendors getting infected first and setting off a chain of infections among community members surrounding the area.”
Based on genomic sequencing of early cases, researchers detected two distinct variants of the virus arising from two infections of humans from animals at the market in November or December 2019. Researchers determined that there were likely many other such transmissions of the virus to humans during that period that never resulted in documented COVID-19 cases.
According to researchers, the studies provide evidence that the virus originated through transmission from animals to humans at the market, with the animals likely being infected by coronavirus-carrying bats in the wild or on farms in China.