Since the start of the COVID-19 pandemic, there has been controversy surrounding the origins of SARS-CoV-2. New research from the University of California, San Diego (UCSD), School of Medicine suggests that the virus likely reached the human epicenter in Wuhan, China, not via bat migration but through the wildlife trade—contradicting hypotheses that SARS-CoV-2 may have emerged from a laboratory.
The researchers used evolutionary modeling techniques to show that the migration of the virus doesn’t support natural dispersal by the native host, horseshoe bats. They instead found that the migration pattern mimicked the route taken by the SARS outbreak in 2002, which was caused by a related virus, SARS-CoV-1. The study published in Cell is titled “The recency and geographical origins of the bat viruses ancestral to SARS-CoV and SARS-CoV-2.”
“At the outset of the COVID-19 pandemic, there was a concern that the distance between Wuhan and the bat virus reservoir was too extreme for a zoonotic origin,” said co-senior author Joel Wertheim, PhD, professor of medicine at UCSD School of Medicine.
Sarbecoviruses—the group of coronaviruses that includes both SARS-CoV-1 and SARS-CoV-2—have long circulated in horseshoe bats across Western China and Southeast Asia. While these viruses are not harmful to their bat hosts, they can infect other animals and humans through zoonotic spillover and are thought to be the ultimate source of both human outbreaks.
Horseshoe bats are the primary host for the ancestor of the viruses that caused both the 2002 SARS outbreak and the COVID-19 pandemic, but a new study suggests that the wildlife trade transported the virus to the places where they first emerged in humans. [Composite image: COVID-19, Greater horseshoe bats, Raffaele Maiorano, CC0 1.0 via iNaturalist; SARS-CoV-2 virus, NAIAD, CC-BY-2.0; palm civet, Rejoice Gassah, CC BY 4.0 via iNaturalist]
The authors write that the direct ancestors of the viruses “are unlikely to have reached their respective sites of emergence via dispersal in the bat reservoir alone.”
“Horseshoe bats have an estimated foraging area of around 2–3 km and a dispersal capacity similar to the diffusion velocity we estimated for the sarbecoviruses related to SARS-CoV-2,” explained co-senior author Simon Dellicour, PhD, head of the Spatial Epidemiology Lab at Université Libre de Bruxelles.
How they reached the emergence sites in humans, over a thousand kilometers away, has remained unclear. To address this, the researchers mapped the evolutionary and geographic history of sarbecoviruses using available genome sequences, focusing on non-recombining regions to accurately trace evolutionary paths.
According to Jonathan E. Pekar, PhD, a postdoctoral researcher at the University of Edinburgh, the researchers found “that the original SARS-CoV-1 was circulating in Western China—just one to two years before the emergence of SARS in Guangdong Province, South Central China, and SARS-CoV-2 in Western China or Northern Laos—just five to seven years before the emergence of COVID-19 in Wuhan.”
These viruses were found far from the human outbreak epicenters not long before human outbreaks occurred. The researchers calculated that because of the large distances and short timing, the most plausible route of transmission was through the wildlife trade via intermediary hosts.
Earlier studies suggested that palm civets and raccoon dogs—animals commonly sold in live-animal markets—played a role in the transmission of SARS-CoV-1 to humans in the 2002 SARS outbreak. This new study provides evidence that SARS-CoV-2 likely followed a similar path.
“The viruses most closely related to the original SARS coronavirus were found in palm civets and raccoon dogs in southern China, hundreds of miles from the bat populations that were their original source,” said co-senior author Michael Worobey, PhD, professor at the University of Arizona.
He continued, “For more than two decades, the scientific community has concluded that the live-wildlife trade was how those hundreds of miles were covered. We’re seeing exactly the same pattern with SARS-CoV-2.”
These findings also challenge a widely circulated alternative narrative that the distance between bat reservoirs and Wuhan supports a lab-origin theory for SARS-CoV-2. Instead, Wertheim points out that this study demonstrates that such a dispersal pattern “isn’t unusual and is, in fact, extremely similar to the emergence of SARS-CoV-1 in 2002.”
The study also emphasizes the dangers of increasing human-animal interactions, particularly through the wildlife trade. The researchers argue that by continuing to sample bat populations and studying viral evolution, it may be possible to predict and prevent future zoonotic spillovers.
“These results can guide future sampling efforts and show that genomic regions nearly identical to SARS-CoV and SARS-CoV-2 were circulating in horseshoe bats,” the authors wrote. “This confirms their importance as a reservoir species and highlights the role of intermediate hosts in bringing these viruses into human populations.”
The post SARS-CoV-2 Likely Spread Through Wildlife Trade, Not Bat Migration appeared first on GEN - Genetic Engineering and Biotechnology News.
The researchers used evolutionary modeling techniques to show that the migration of the virus doesn’t support natural dispersal by the native host, horseshoe bats. They instead found that the migration pattern mimicked the route taken by the SARS outbreak in 2002, which was caused by a related virus, SARS-CoV-1. The study published in Cell is titled “The recency and geographical origins of the bat viruses ancestral to SARS-CoV and SARS-CoV-2.”
“At the outset of the COVID-19 pandemic, there was a concern that the distance between Wuhan and the bat virus reservoir was too extreme for a zoonotic origin,” said co-senior author Joel Wertheim, PhD, professor of medicine at UCSD School of Medicine.
Sarbecoviruses—the group of coronaviruses that includes both SARS-CoV-1 and SARS-CoV-2—have long circulated in horseshoe bats across Western China and Southeast Asia. While these viruses are not harmful to their bat hosts, they can infect other animals and humans through zoonotic spillover and are thought to be the ultimate source of both human outbreaks.
Horseshoe bats are the primary host for the ancestor of the viruses that caused both the 2002 SARS outbreak and the COVID-19 pandemic, but a new study suggests that the wildlife trade transported the virus to the places where they first emerged in humans. [Composite image: COVID-19, Greater horseshoe bats, Raffaele Maiorano, CC0 1.0 via iNaturalist; SARS-CoV-2 virus, NAIAD, CC-BY-2.0; palm civet, Rejoice Gassah, CC BY 4.0 via iNaturalist]
The authors write that the direct ancestors of the viruses “are unlikely to have reached their respective sites of emergence via dispersal in the bat reservoir alone.”
“Horseshoe bats have an estimated foraging area of around 2–3 km and a dispersal capacity similar to the diffusion velocity we estimated for the sarbecoviruses related to SARS-CoV-2,” explained co-senior author Simon Dellicour, PhD, head of the Spatial Epidemiology Lab at Université Libre de Bruxelles.
How they reached the emergence sites in humans, over a thousand kilometers away, has remained unclear. To address this, the researchers mapped the evolutionary and geographic history of sarbecoviruses using available genome sequences, focusing on non-recombining regions to accurately trace evolutionary paths.
According to Jonathan E. Pekar, PhD, a postdoctoral researcher at the University of Edinburgh, the researchers found “that the original SARS-CoV-1 was circulating in Western China—just one to two years before the emergence of SARS in Guangdong Province, South Central China, and SARS-CoV-2 in Western China or Northern Laos—just five to seven years before the emergence of COVID-19 in Wuhan.”
These viruses were found far from the human outbreak epicenters not long before human outbreaks occurred. The researchers calculated that because of the large distances and short timing, the most plausible route of transmission was through the wildlife trade via intermediary hosts.
Earlier studies suggested that palm civets and raccoon dogs—animals commonly sold in live-animal markets—played a role in the transmission of SARS-CoV-1 to humans in the 2002 SARS outbreak. This new study provides evidence that SARS-CoV-2 likely followed a similar path.
“The viruses most closely related to the original SARS coronavirus were found in palm civets and raccoon dogs in southern China, hundreds of miles from the bat populations that were their original source,” said co-senior author Michael Worobey, PhD, professor at the University of Arizona.
He continued, “For more than two decades, the scientific community has concluded that the live-wildlife trade was how those hundreds of miles were covered. We’re seeing exactly the same pattern with SARS-CoV-2.”
These findings also challenge a widely circulated alternative narrative that the distance between bat reservoirs and Wuhan supports a lab-origin theory for SARS-CoV-2. Instead, Wertheim points out that this study demonstrates that such a dispersal pattern “isn’t unusual and is, in fact, extremely similar to the emergence of SARS-CoV-1 in 2002.”
The study also emphasizes the dangers of increasing human-animal interactions, particularly through the wildlife trade. The researchers argue that by continuing to sample bat populations and studying viral evolution, it may be possible to predict and prevent future zoonotic spillovers.
“These results can guide future sampling efforts and show that genomic regions nearly identical to SARS-CoV and SARS-CoV-2 were circulating in horseshoe bats,” the authors wrote. “This confirms their importance as a reservoir species and highlights the role of intermediate hosts in bringing these viruses into human populations.”
The post SARS-CoV-2 Likely Spread Through Wildlife Trade, Not Bat Migration appeared first on GEN - Genetic Engineering and Biotechnology News.