Astandard device in detective stories is a map on which certain buildings are circled. Their locations are thought to be revealing, though often they just create a false trail. When four of the first cases of a strange, pneumonia-like illness seen in Wuhan, China, in December, 2019, were found to have a connection to the Huanan Seafood Wholesale Market, it seemed a key to solving the mystery of the illness’s origin. Live animals were reportedly on sale there, offering a route for pathogens to jump from wild species to humans. But then other cases, some of them earlier, were identified, with no known connection to the market. In due course, more sites were circled on the pandemic map. One was the Wuhan Institute of Virology, which contains a Biosafety Level 4 lab. The institute’s work included experiments on the bat coronaviruses that are among the closest known relatives to sars-CoV-2, which causes covid-19.
The Battle Over the Coronavirus LabLeak Theory
Illustration by João Fazenda

The market and the institute have at times served as shorthand for two broad sets of possible answers about the origin of the virus: that it was “zoonotic,” meaning that it travelled directly from animals, or that it was transmitted by an accidental “lab leak,” from a place such as the Wuhan Institute. On May 26th, President Joe Biden, in a statement, described U.S. intelligence agencies as being uncertain about which scenario is more likely, with a majority of them believing that firm evidence for either is lacking. Biden asked them to “redouble their efforts” and come back with a better answer in ninety days.

The debate has become, to an unfortunate degree, loud, contentious, and infused with politics. Former President Donald Trump has insinuated that the Chinese government intentionally spread the virus as part of a plan to have it take hold in this country and destroy our economy. Republican members of Congress have turned a recently disclosed e-mail mentioning a possible lab source, which Anthony Fauci received in February, 2020, into yet another argument for firing him, apparently because he didn’t instantly condemn Beijing. Earlier this month, Fauci told the Financial Times that he still thinks it’s most likely that the coronavirus jumped species, but that “we need to keep on investigating until a possibility is proven.”

The Chinese government has not helped by failing, at almost every stage, to respond transparently to questions or to share information. Beijing’s decision, earlier this year, to seriously constrain the work of an investigation sponsored by the World Health Organization meant that the resulting report, which perfunctorily dismissed the lab-leak theory, was not seen as credible. (The director-general of the W.H.O. pointedly told member states, “All hypotheses remain on the table.”) There is some concern that exploring the theory will further incite xenophobia—with China being blamed for every consequence of a pandemic that the United States also failed to control. Yet Chinese citizens have consistently pushed back against censorship, often at personal risk. According to official figures, covid-19 has killed almost four million people; a study by The Economist concludes that the true number may be close to thirteen million. Partisanship, in whatever form, can’t be the guide here.

From the beginning, it made sense that sars-CoV-2 would have a zoonotic origin, because that is how other novel pathogens, such as the viruses causing Ebola, sars, and mers, have emerged. The genome of sars-CoV-2 implies that it is descended from a coronavirus that infected a horseshoe bat, but when it was identified in Wuhan it had already adapted very well to infect humans. This may suggest that it spent time either in another animal—sars and mers are believed to have moved from bats to civets and camels, respectively, before reaching humans—or in people elsewhere. An intermediate population hasn’t been identified, but there are a lot of places to look: even if Huanan Seafood is not the source, there are more than a dozen markets selling live animals in the city. Wuhan is a metropolis of eleven million inhabitants, and it is crisscrossed by travellers, with an international airport and an expansive subway system. It’s worth noting that the natural zoonotic path for novel pathogens often relies on some distinctly unnatural disruption, such as climate change, poaching, or urban sprawl, to spur encounters between species.

Meanwhile, “lab leak” has come to describe at least two related theories. The first starts with the observation that the Wuhan Institute has worked with bat coronaviruses; its researchers have collected samples from sites hundreds of miles away, including a disused mine where, in 2012, six workers fell ill with sars-like symptoms. All that activity involved a great deal of interaction between researchers, locals, and many bats, and in that context it’s conceivable that a novel virus could emerge, or be transmitted, or be collected and then accidentally mishandled. This might be better called the “lab nexus” theory, because it envisions the lab as a crossroads for people and viruses. According to information from a U.S. intelligence report published by the Wall Street Journal, three workers at the institute became sick in November, 2019, with symptoms consistent with both covid-19 and seasonal illnesses, and sought hospital care. Fauci has said that he’d like to see their medical records.

The scientific work itself—some of which benefitted from National Institutes of Health funding—forms the basis for what might be called the “lab-experiment leak” theory. The Wuhan Institute is one of a number of labs around the world, including in Europe and the United States, that have engaged in “gain of function” studies. This means that viruses are in some way engineered, in many cases to make them more infectious or more virulent. The idea—and there is disagreement about whether it is a good one—is that doing so will better prepare scientists to fight future viruses. But, in the short run, additional novel pathogens are in close proximity to humans; the provocative question is whether sars-CoV-2 was one of them. Scientists who have examined its genome are divided about whether it shows signs of engineering, specifically in an area known as the “furin cleavage site,” and about whether such signs would even be discernible. A leading scientist at the Wuhan Institute, Shi Zhengli, known as the Bat Woman, has said that she is confident that the virus was not one worked on in her lab.

There are wilder theories, too, involving intimations of biowarfare plots. But, although the lab-leak scenario figures in many conspiracy theories, it is not itself a conspiracy theory; the consensus is that it is unproved, but plausible. That possibility alone should prompt serious reflection on the practices in virological labs. Yet what is striking is that none of the theories are reassuring. Each implicates something about how we, collectively, live on the planet. And each suggests that many things need to change. ♦