A groundbreaking study conducted by an international team reveals that bat viruses closely linked to SARS-CoV-1 and SARS-CoV-2 likely emerged far from outbreak locations. This finding suggests that wildlife trade, rather than natural bat migration, played a crucial role in facilitating these viruses' entry into human populations. The research highlights the speed at which these viruses spread compared to typical bat virus dispersal rates and emphasizes the significance of wildlife trade as a vector for zoonotic transmission.

The analysis underscores the importance of continuous surveillance of sarbecoviruses in bats and high-risk wildlife to prevent future outbreaks. By reconstructing the evolutionary history of these viruses, the researchers identified their origins and movement patterns across Asia, offering insights into how human activities contribute to zoonotic spillover events.

Accelerated Spread: Viruses Moving Faster Than Bats

Researchers discovered that ancestral viruses leading to SARS outbreaks traveled significantly faster than typical bat-borne viral spread rates. These viruses moved at speeds 10–100 times greater than what natural bat behavior could explain. This rapid movement highlights the inadequacy of natural dispersal mechanisms alone in explaining the emergence of pandemics.

Through advanced genetic recombination detection and Bayesian phylogeographic modeling, scientists reconstructed the evolutionary history of SARS-related coronaviruses. They found that while sarbecoviruses have circulated in bat populations across Western China and Southeast Asia for millennia, the closest inferred bat virus ancestors of SARS-CoV-1 and SARS-CoV-2 emerged less than a decade before each pandemic. These viruses would need to travel over 1,000 kilometers to reach their human emergence sites, a journey implausible through natural bat dispersal alone. Instead, human-mediated factors such as wildlife trade are implicated as the driving force behind this accelerated movement.

Wildlife Trade: Bridging the Gap Between Bats and Humans

The study concludes that wildlife trade, rather than bat migration, transported these viruses into human populations. For SARS-CoV-1, palm civets and raccoon dogs commonly found in live-animal markets likely served as intermediate hosts bridging the gap between bats and humans. This pattern is mirrored with SARS-CoV-2, underscoring the critical role of wildlife trade in facilitating zoonotic spillover events.

By examining hypothetical unsampled viral diversity, researchers confirmed that their findings remain robust even if closer relatives existed in under-sampled regions. The study emphasizes the transnational risk posed by wildlife trade in driving zoonotic spillovers. Continuous surveillance of sarbecoviruses in bats and high-risk wildlife, particularly in northern Laos and southwestern China, is essential to preventing future outbreaks. This international collaboration not only resolves longstanding questions about the origins of SARS coronaviruses but also highlights how pathogens can travel far beyond their natural reservoirs through human activities, urging global action to mitigate such risks.