Wildlife trade could transport Covid-19 virus to humans, study found

A new study published in cells on May 7, 2025 shows that the virus of Covid-19 spreads too quickly from its origins to be naturally carried by bats. Instead, the researchers concluded that the wildlife trade could transport SARS-COV-2 to Wuhan, reflecting the path taken by the virus responsible for the 2002 SARS outbreak.

Tracking virus movement through evolutionary history

Researchers at the University of California, San Diego and several international institutions analyzed the evolutionary history of SARS-COV-1 and SARS-COV-2 by examining genomic sequence data. Their analysis faces a key challenge: These viruses are often recombined within the host, making their evolutionary path difficult to track.

“When two different viruses infect the same bat, sometimes the amalgam of two different viruses appears from the bat,” said Dr. Joel Wertheim, a professor at the San Diego School of Medicine and co-training author of the study.

The team overcomes this obstacle by identifying non-recombinant regions of the viral genome to reconstruct accurate evolutionary history. Their findings clearly depict how these viruses crossed in Asia before jumping into humans.

Geography and timing reveal modes of transportation

The study identified China or northern Laos as a possible origin of SARS-COV-2 ancestors. From there, the virus will need to travel up to 2,700 kilometers to reach Wuhan in central China, where the pandemic was on the 19th. Similarly, SARS-COV-1’s ancestors arrived in Guangdong Province from western China, which then caused the outbreak in 2002.

What makes these findings reveal in particular is the timing. The researchers determined that the ancestors of SARS-COV-2 left their origin only 5-7 years before Covid-19 appeared in humans. For SARS-COV-1, this timeline is even shorter, only 1-2 years.

When comparing these travel patterns with typical bat movements, the researchers found a surprising mismatch. Although the virus usually spreads at a speed consistent with horseshoe bat movements (foraging within 2-3 kilometers of the habitat), their last stop to the population center occurs too quickly because natural bats are dispersed.

Wildlife Transactions as Missing Links

The researchers concluded that the wildlife trade may play a crucial role in transporting both viruses to their sites of occurrence. This matches existing evidence about SARS-COV-1, which was previously shown by previous studies, was conducted from Yunnan to Guangdong via infected palm branches or raccoon dogs, which are commonly used in fur and meat.

“The virus that is most closely associated with the original SARS coronavirus was found in palm branches and raccoon dogs in southern China, hundreds of miles from the bat populations they originally originated from,” explains Dr. Michael Worobey, a professor at the University of Arizona and associate degree. “Over twenty years, the scientific community has concluded how the trade in on-site wildlife covers hundreds of miles. We see exactly the same pattern as SARS-COV-2.”

These findings address the problem caused by speculation about the origin of SARS-COV-2 laboratory.

“At the beginning of the pandemic in 19009, people were concerned that the distance between Wuhan and the bat virus reservoir was too extreme for zoonotic origins,” Wertheim noted. “This article shows that it is not uncommon and is actually very similar to the emergence of SARS-COV-1 in 2002.”

Impact on future pandemic prevention

Zoomytic spillover events (diseases from animals to humans) are increasing due to wildlife trade, urbanization and habitat destruction. Researchers believe that continuous sampling of wild bat populations can help identify potential sources of future coronavirus outbreaks.

By understanding the evolutionary history and transmission patterns of these viruses, scientists hope to better prepare and control future disease outbreaks. The study highlights the importance of monitoring wildlife trade networks as a potential pathway for emerging infectious diseases.

Key findings:

• The ancestors of SARS-COV-2 originated in western China or northern Laos, 5-7 years ago, during the COVID-19 pandemic
• The virus spreads up to 2700 kilometers and arrives in Wuhan, too fast to spread natural bats
• SARS-COV-1 shows a similar pattern, moving from western China to Guangdong in just 1-2 years
• SARBECOVIRAS is usually at a speed that matches the movement of horseshoe bats (2-3 km)
• Wildlife trade may have transported both viruses through intermediate animal hosts
• These findings support similar natural origins of SARS-COV-1 and SARS-COV-2