A recent article in the academic journal Science has attracted attention for its detailed modeling of the initial post-emergence of the virus SARS-CoV-2 and the disease it causes, COVID-19. The authors of this study have touted it as ending the debate about the origins of the novel coronavirus, favoring a zoonosis, or a jump from an animal host to humans without any steps in between.
As important as it is to understand the early dynamics of COVID in Wuhan, China, the coronavirus did not spontaneously generate itself in market stalls in Wuhan, nor does the Science article suggest otherwise. Here are four epidemiological (not virological, not science-political) questions that still deserve answers.
First, from what animal species did SARS-CoV-2 make the jump to humans? Yes, the coronavirus was found in the Huanan Seafood Market in Wuhan. Yes, much can be said about its spread there. Eventually, it spread the world over, many times. Which specific animal(s) brought the virus to the market? Finding a virus anywhere in the market once transmission began is no substitute for identifying the core zoonotic event that unleashed COVID on the world.
Second, where are the animals in China with SARS-CoV-2 antibodies or infection? After its emergence, SARS-CoV-2 has found hosts in farmed mink, pet hamsters, and in white-tailed deer of the eastern U.S., in which it is now enzootic. Where, then, is the SARS-CoV-2 infection in Chinese wildlife? If it came to the seafood market in an animal raised, trapped, or hunted for human consumption, there must be more examples in the wild.
Third, why Wuhan? The typical response is some version of, “It could have been any city in China, since they all have wet markets. It just happened to be Wuhan.” This hand-wave argument is as persuasive as saying, “Cancer happens. There just happens to be a cluster of cases on top of this Superfund site.”
Bats in Laos are most likely the host of ancestor viruses that would become the novel coronavirus. Where is the COVID co-emergence in other cities (yes, with wet markets) between the China-Laos border and Wuhan?
Fourth, why is it considered epidemiologically unusual that the origin may have been a lab escape from a gain-of-function experiment? As Alison Young has amply documented, accidents and safety lapses happen so frequently at containment labs that they are considered normal.
We know the Wuhan Institute for Virology, a global center for coronavirus research, is not far from the Huanan market. It was part of a proposal, called DEFUSE, on gain-of-function coronavirus research. The proposal was not funded, but there has not been much transparency on what research was actually performed at the institute.
Opposing the risks of gain-of-function virus research was uncontroversial enough in 2014 for many leading researchers to sign the Cambridge Working Group statement against this inherently risky practice.
Will we ever know the answers to these four questions? As long as the Chinese Communist Party is in power, probably not.
This pivots to a fifth question, epistemological rather than epidemiological: What do things look like when the burden of proof, instead of the weight of assumed validity, falls on the zoonotic theory of COVID emergence? It’s not unreasonable to say, “Prove the lab leak,” but given the lack of transparency by the institute and its American supporters such as the EcoHealth Alliance, collecting evidence is hard. It is equally reasonable to say, “Prove the zoonosis theory.”
Science doesn’t automatically privilege one hypothesis over another — although some scientists do.
Andrew Noymer is an epidemiologist and medical demographer at the University of California, Irvine, where he is associate professor in the Department of Population Health and Disease Prevention.
