Did the global pandemic seep from a truckbed crowded with animal cages on its way to market? A cave where villagers dig bat guano? A mislabeled vial in a Chinese coronavirus lab?
Those theories have spun into a blame game and a geopolitical battleground. But for scientists, finding the original source of SARS-CoV-2, the virus that causes COVID-19, is key to understanding how to predict, prevent and contain future pandemics that may arise, whether from a leak at one of a growing number of pathogen labs or the accelerating encroachment of humans on the natural world.
Pinpointing the origin of a virus is critical to marshaling a quick response that could save lives and protect economies — especially in the early days of an outbreak. Evidence of a natural spillover would drive efforts to limit human interaction with wild animals and set up a stronger surveillance system. A lab origin would intensify demands for strict international standards for types of research and the conditions under which they should be done.
"The question isn't who to blame — it's whether you want another virus to kill millions more people in the next decade," said Alina Chan, a molecular biologist at the Broad Institute of MIT and Harvard, who has advocated for a deeper investigation into the pandemic's source. "When your house catches on fire, it shouldn't be controversial to look closely at how it happened."
As we bulldoze rainforests, heat the climate and consume exotic species, we run the risk of snipping a thread in a web stretched too thin, unleashing "Disease X" and watching it move nimbly through its new hosts and into us. That's what happened with Ebola, SARS and MERS. And it'll happen again.
Disruptive and deadly as they were, those outbreaks failed to dramatically change how we recognize and fight emerging dangers. If a transmission from animal to human proves to have caused the coronavirus contagion that killed 3.5 million globally and robbed the U.S. economy of some $16 trillion, ecologists may finally get the financial and strategic backing to map the planet's viral landscape, anticipate hot spots, and train teams to recognize early clusters of disease.
Linking early cases of SARS to palm civets led to a crackdown on restaurants serving the delicacy; understanding MERS transmission spurred efforts to develop a vaccine for camels. The threat of bird flu to humans has changed poultry farming practices worldwide. Likewise, if SARS-CoV-2 spread from a wet market or an animal, as most scientists suggest, it would affect future strategy.
So far, though, there is no clear sign of an intermediate host. Of the 80,000 animal samples tested in China, none have contained the virus' genetic material or antibodies to it.
But evidence of an accidental lab leak would have far different implications, particularly for the almost 60 BSL-4 labs that are planned or operating in 23 different countries. BSL-4 — or biosafety Level 4 — labs have the highest level of biocontainment as researchers are working with dangerous or easily transmissible pathogens.
Only about a fourth of the countries operating, or planning to operate, such labs score well on biosafety preparedness criteria, and more than three-quarters of the labs are in crowded urban settings, increasing the likelihood of an accidental leak.