A Recent Study Indicates That Wildlife Trade, Rather Than Bats, Likely Transmitted SARS-CoV-2 to Wuhan
A significant study released in Cell on May 7, 2025, provides fresh insights into the origins of the virus behind the COVID-19 pandemic. Researchers from UC San Diego, along with an international team of scientists, suggest that SARS-CoV-2—the virus linked to COVID-19—migrated too quickly and over too great a distance to have arrived in Wuhan, China solely through natural bat migration. Their findings strongly imply that the wildlife trade likely acted as a swift conduit for the virus’s entry into the city, mirroring patterns observed during the 2002 SARS outbreak.
Tracking the Virus’s Journey Through Evolution
To gain a better understanding of the intricate routes through which deadly viruses like SARS-CoV-2 and its predecessor SARS-CoV-1 entered human populations, researchers analyzed genetic information covering the evolutionary histories of both viruses. A significant hurdle in this endeavor was the propensity of coronaviruses to recombine—exchanging segments of genetic material while residing in their animal hosts, which complicates their lineage.
“When two different viruses infect the same bat, often what emerges is a hybrid incorporating segments from both,” noted Dr. Joel Wertheim, co-senior author and a professor at the UC San Diego School of Medicine. This viral recombination complicates the identification of clear evolutionary connections, hindering the tracing of their origins.
To overcome this challenge, scientists concentrated on “non-recombining regions” of the viral genomes—sections that have remained genetically stable over time. By crafting more precise family trees for these viruses, researchers were able to outline the ancestral routes across Asia that led to human outbreaks.
Geographic and Chronological Evidence Highlights Transportation Routes
The study identifies the most recent ancestor of SARS-CoV-2 as originating from areas in western China or northern Laos. However, the virus then needed to traverse over 2,700 kilometers to reach Wuhan in central China—where the first significant COVID-19 cases were detected in late 2019.
SARS-CoV-1, the pathogen responsible for the 2002-2003 SARS epidemic, took a remarkably similar path. It originated in western China and traveled to Guangdong Province in southern China, covering a considerable distance before initiating human infections.
Timing provides another critical clue. Researchers calculated that the ancestor of SARS-CoV-2 appeared approximately 5-7 years before the onset of the pandemic. In comparison, the precursor to SARS-CoV-1 moved along an even tighter timeline—taking only 1-2 years before its jump into humans.
Such rapid movement over vast distances implies that neither virus could have feasibly traveled through bat populations alone. Horseshoe bats, which are common hosts for sarbecoviruses (the subgenus that includes both viruses), generally have small foraging territories of 2-3 kilometers and slow dispersal habits. Consequently, these findings challenge the notion that natural bat-to-bat transmission could explain the viruses’ paths.
Wildlife Trade as a Likely Transport Mechanism
Rather, the study suggests that the wildlife trade likely played an essential role in closing the gap between viral reservoirs and densely populated human areas.
This conclusion aligns with earlier research on SARS-CoV-1, which connected its emergence to palm civets and raccoon dogs sold for meat and fur in live-animal markets. These animals acted as intermediary hosts, acquiring the virus from bats in their natural habitats and transferring it across provinces through human commerce.
“The viruses most closely related to the original SARS coronavirus were discovered in animals—civets and raccoon dogs—hundreds of miles away from their bat ancestors’ habitats,” stated Dr. Michael Worobey, co-senior author and professor of evolutionary biology at the University of Arizona. “The only reasonable explanation was that they were carried by the wildlife trade. We now observe this same trend repeating with SARS-CoV-2.”
This revelation also addresses previous doubts concerning a purely natural origin for SARS-CoV-2. Given the considerable geographic distance between Wuhan and the southern Chinese bat populations, speculation about laboratory-related scenarios had emerged. This study demonstrates that such distances are not only feasible under a wildlife trade model but have already been documented in prior coronavirus outbreaks.
Consequences for Future Pandemic Prevention
The research highlights the significant role that human activities—particularly the trade and sale of wild animals—play in precipitating zoonotic spillover events, where viruses jump from animals to humans. As global urbanization, deforestation, and live-animal trade networks expand, so does the risk of future pandemics arising in similar manners.
To combat this escalating threat, the researchers advocate for:
– Continuous sampling and monitoring of wild bat populations in Asia and elsewhere to keep pace with emerging viruses.
– Enhanced surveillance of intermediary animal hosts, especially those engaged in wildlife farming and trade.
– Stricter regulation and oversight of wildlife markets, particularly those trafficking known zoonotic carriers like civets and raccoon dogs.