There is really no explanation other than that the virus started spreading to the human population in this market In the Science paper, which began life as a preprint in February before undergoing peer review, you say the Huanan seafood wholesale market in Wuhan was the “early epicenter” of the Covid-19 pandemic. To be clear, are you saying that Huanan Market was the source of the pandemic? That’s largely what the research suggests. We are not able to pinpoint the exact spillover event, the exact animal from which the virus passed to humans, but there is really no other explanation for what our analysis shows. And that is that there were no cases of Covid-19 in Wuhan or anywhere else before these early cases that we looked at, which are closely linked to the market. What does your document add that is new? No one disputes that there were many early market-related cases. The question was, could the virus come from somewhere else and have just been amplified in the market? First, we did a lot of detective work to see if there was a geographic connection between these early cases. Their geospatial coordinates were available, but no one had done this kind of analysis before. Importantly, when we excluded the first cases that were directly related to the market – meaning the patient was there – the association with the market became even stronger. This is consistent with the virus acquiring the ability to transmit from person to person in the market, so that people who had not been there began to catch it from those who had. It radiated like ripples on a lake. Workers in protective clothing at the Huanan Seafood Wholesale Market in Wuhan, China, in March 2020. Photo: Héctor Retamal/AFP/Getty Images Second, we know as of June 2021 that many kinds of live animals were for sale in Huanan. We obtained market plans and legal and business records on the items sold at the various stalls and cross-referenced them with data from the Chinese Center for Disease Control and Prevention (CCDC) on swabs taken from market surfaces in early 2020, found positive for Sars-CoV-2 – the virus that causes Covid-19. These positive samples were collected in the section of the market where the live animals were sold. they came from cages, carts and equipment that had come into contact with these animals. This was not widely known. By a crazy coincidence, in 2014 one of my co-authors, Edward Holmes, had taken a photo showing a particular stall where live raccoon dogs – which are susceptible to Sars-CoV-2 – were kept in cages stacked in a cart. He took the photo while being shown around the market by Chinese scientists who deemed him to be at high risk of viral transmission. This stable later produced five samples positive for Sars-CoV-2. Finally, we have shown that many of the items sold in the market are susceptible to infection by Sars-CoV-2. We were the first to put all that evidence together and say that when you look at the whole picture, there’s really no explanation other than that the virus started to spread through the human population in that market. There was a companion paper to yours in the same issue of Science. What did this show? In the first cases the virus already existed in two distinct lineages, A and B – although confusingly, B was the older of the two. Until February this year it was believed that only the B lineage was present in the Huanan market, but then a team led by George Gao, the former head of the CCDC, showed that the A lineage was also there. [this paper is undergoing peer review]. The accompanying paper, by Jonathan Pekar of the University of California, San Diego and colleagues – which I did not deal with – reconstructs their family tree to show that they probably reached humans as a result of two separate transmission events within a few weeks of each other the other one. Now, if the virus had escaped from a lab, someone would have to become infected with lineage B in the lab, go to the market and infect people there without infecting anyone along the way, and then someone else would have to do the exactly the same as lineage A a few weeks later. It’s not impossible, but a simpler explanation is that the virus was released into the market in one animal, from where it spread to other animals, diverging along the way. The two lineages then poured out separately into humans. No meaningful further study will take place without Chinese cooperation, and this debate has hurt the chances of that happening. One of the criticisms of your paper is that you remain vague about “subsequent events” – that is, how the virus got to market in the first place. That’s one thing we don’t know. We know that the live animal trade uses a common supply chain. Animals are gathered from all over, including the far reaches of China, and brought to market. There may well have been other upstream spillover events, but the other thing to keep in mind about the market is that it is an environment where human-to-human transmission can be established and maintained – because there are many animals housed in close contact with each other, and lots of people hanging around them. Dissemination events in remote, sparsely populated areas are more likely to be dead ends because there are very few susceptible human hosts. We also know that when a related coronavirus, Sars, emerged in China 20 years ago, it was linked to the live animal trade. Have you ruled out that a lab leak caused the pandemic? I don’t think you could ever completely rule it out, but we’ve proven pretty convincingly that it came from the market. Could you learn more? Yes. We are still trying to establish the susceptibility to Sars-CoV-2 of the different items sold in the market. I would like to see information about the farms where the animals were raised and any samples taken from those animals before the farms were closed and bought and the animals killed. These may allow us to identify the intermediate host – the animal from which the virus likely jumped to humans. I would be curious to see human serology data as well, to see if people working in the live animal trade in 2019-20 had elevated levels of Sars-CoV-2 antibodies in their blood. It is possible that this information exists and we are not given access to it, and this is one of the most difficult things to discuss with people who support the lab leak theory. Looking at it from the Chinese government’s point of view, though, it’s actually worse if it comes from the market. After Sars they were supposed to crack down on the live animal trade, so it’s a real shame for them to have the same thing happen again – especially in a city where world-class coronovirologists work. One thing is clear: no meaningful further study will take place without Chinese cooperation, and this debate has hurt the chances of that happening. Some scientists advocating a natural origin have been accused of a conflict of interest, generally because they have worked with Chinese scientists, including researchers working at the Wuhan Institute of Virology — the institution most often cited as the source of a purported lab leak. Do you have a potential conflict of interest? I have never worked with the Wuhan Institute of Virology. I have never had grants to work in China and I have never been to China. However, I have been accused of a conflict of interest, for the work I have done on Mers and Ebola that was funded by the US Department of Defense. Some of the wildest conspiracy theories involve US biodefense. What should we take away from this debate about origins? Every time a new virus appears, there is a debate about its origin. It is important to have this, but there is often an unrealistic expectation that the explanation will be simple. Some of the language doesn’t help – the term ‘patient zero’, for example. If there have been multiple transmission events, it may not be theoretically possible to identify the first person who became ill. You can never completely prevent the politicization of the debate, but you can make the analyzes that are more likely to convince serious scientists. Some critics will never be satisfied. In the case of Sars-CoV-2, they are twisting into ever more complicated logic cookies to keep the lab leak theory alive. You’ve been a Twitter warrior throughout and the conversation has been toxic at times. How was that? If I had known what it would be like, I probably would never have opened my mouth. I’ll also point out that there’s a reason there aren’t many female co-authors on this article. We all get personal attacks, but men are accused of being corrupt or evil, while we are also accused of being ugly, fat, old, mean. I had threats of rape and death. I had to call the police. I have pretty high self-esteem, but it wears you down. Does Twitter need to be configured? Twitter has good and bad sides. It can be a great place to talk about science, to reach audiences you wouldn’t normally reach, to meet colleagues. That’s how I heard about my current job and yesterday I got a grant for a partnership that started on Twitter. That’s how I came…
