What the heck, everything’s so quiet and uneventful – let’s revisit the origin-of-Covid controversy, what do you say? The two main contenders have been the original “zoonotic crossover in a market that slaughtered animals” and the “leaked out of the Wuhan Institute of Virology” one. I have been agnostic about this, but I have to clarify that when I give the latter possibility thought it does not imply that I think that this was in any way an engineered virus. I have seen no convincing evidence of that, and a lot of evidence to the contrary. No, for me, it’s always come down to “random jump into humans, in an environment that certainly favors it” versus “bad lab technique, which can and does happen all the time”.
This new preprint has a lot of interesting information in it that strongly suggests that the Wuhan-market hypothesis is correct. It’s from a large multicenter group of very well-qualified virologists, physicians, and biologists of many types, and it is a serious effort to nail down this question. A compelling line of argument in it is geographical:
In this study, we use epidemiological, genomic, commercial, photographic, location, social mobility and survey data – from a range of sources – to investigate the hypothesis that the COVID-19 epidemic in Wuhan began at the Huanan market. We conclude that the Huanan market was indeed the epicenter of COVID-19 emergence. We demonstrate that December 2019 COVID-19 cases were geographically distributed unexpectedly near to, and centered on, the Huanan market, irrespective of whether or not they worked at, had visited, or were knowingly linked to someone who had visited this market in late 2019. Furthermore, of those cases epidemiologically linked to the market, the overwhelming majority were specifically linked to the western section of the Huanan market, where most of the live-mammal vendors were located. Validating this spatial link between live animals and human COVID-19 cases, we show that positive environmental samples distinctly associated with animals clustered within a small area of the Huanan market where live mammal sales were most concentrated.
That’s getting down to some pretty fine detail, and remember, the Wuhan Institute of Virology is in a completely different part of town, across the Yangtze River and about 9 miles away as the crow flies (or as the virus wafts, if you prefer). The preprint goes into the confusion in the early days of the viral outbreak in late 2019 – indeed, some of the reported early cases don’t seem to have actually come down with the virus until much later in December, and it’s for sure that many other cases were missed. There were doubts about human-to-human transmission of the virus, and then there was a theory on the other end of the spectrum that the market-centered cases just represented an easier-to-document human-to-human spreading event rather than a zoonotic spillover from the animal tissues found there. By January, it was becoming clear that there had been a really substantial undercount of cases (since the disease presented – and still presents – with varying severity).
The authors have 156 December cases with location information, and a majority of these cluster on the west side of the Yangtze (instead of the east side, where the virology facility is). And as mentioned above, these are at the highest density around the Huanan market itself. Medical history fans will immediately think of John Snow identifying the water pump in London that was spreading cholera by mapping the cases, and see Figure 1 in the preprint (reproduced at right). The paper also examines data from China’s Weibo social media platform of cases in January and February, and although these have certainly spread more across the city, they still show density around the market epicenter. And adjusting for the time of the reports shows that the earlier the case, the more likely it is to be associated with the market.
There’s also an examination of the hypothesis mentioned above, whether or not the cluster around the market was merely a workplace-spreading event that came up out of a disease that might have already been quietly widespread in the city. A null hypothesis map, just based on population density (what you would expect from the “cryptic disease” situation) does not generate anything like the observed data, and in fact make the observed case data extremely unlikely. In fact, the density of elderly people who were at greatest risk of catching the disease (and of showing overt symptoms) is much higher in many other parts of Wuhan than it is where the disease actually made itself known. If the disease were hidden but widespread, or spreading from another source entirely, then there are uncountable other busy population-density areas that should have shown up in the data.
The paper has some compelling evidence that the Huanan market (and others in the city) were indeed selling (and butchering) a wide variety of animals. One of the authors visited these several times in the 2017-2019 period (before the pandemic, of course) and noted at least 38 species, including 31 that are supposedly protected and illegal to trade. As an animal conservationist myself, I will stop to roll my eyes and groan at this fact, but move on. Several of these species are now known to be susceptible to the SARS-Cov-2 virus and capable of transmitting it, particularly raccoon dogs (Nyctereutes procyonoides). This is not a new thing.
So there is a great deal of evidence favoring the market hypothesis. The only other way that I can think of to easily explain these data would be systematic deception on the part of the Chinese authorities. That’s not a paranoid statement – the Chinese government is systematically deceptive. After all, they bulldoze Uighur villages and ship the residents off to concentration camps that are visible from low Earth orbit, all the while denying that nothing is happening except perhaps some happy, smiling re-education here and there. No, the Chinese government is capable of treating its own people in the same fashion that the Wuhan merchants treat their raccoon dogs. But as the preprint notes, the authorities have attempted to be deceptive about the market hypothesis as well. So the idea that the government would plant evidence to implicate the Huanan Market doesn’t make much sense:
In fact, the WHO mission members were told that no unlicensed or live-trapped wild animals had been for sale at the Huanan market and that “no verified reports of live mammals being sold around 2019 were found” (9). Notably, none of the live (known to be susceptible) mammals from species we identify here as present at the Huanan market in November and/or December 2019 have been reported to have been tested for evidence of SARS-CoV-2 infection. The only live mammals ‘from’ the market among the 188 appear to have been animals such as stray cats, dogs, snakes, rabbits, and mice.
The huge bulk of animals tested for the virus in China were things like chickens, cattle, pigs, and other species that have not been implicated in coronavirus transmission at all. The market itself and the (putatively illegal) animal ranches that supply it and others were rapidly shut down by the government, and if they tested animals and/or human workers in this supply chain then no one outside the Chinese bureaucracy has heard about it. But what we do have are reports of environmental samples from inside the market, via a report from China’s CDC:
Of particular salience, we found that five SARS-CoV-2-positive environmental samples were taken from a single stall known to be selling live mammals in late 2019 (Table S2). This level of positivity was matched only by a stall adjacent to it, also with five positive samples (Table S2). Importantly, the objects that tested positive from the stall selling live mammals showed clear associations with animal sales: a metal cage that was situated in a back room, two carts (of the kind frequently used to transport mobile animal cages) and a hair/feather remover (Table S2). No human COVID-19 cases were reported there (9, 15). Remarkably, this was the same stall where one of us (E.C.H.) observed live raccoon dogs housed in a metal cage in 2014, stacked directly on top of a cage of live waterfowl or poultry (39) (Fig. 3E). A common trash cart directly outside of this specific lane was also found to be positive. . .
It’s worth remembering that the CCDC initially identified the market as the source of the epidemic, and then later reversed itself, saying that the market was “one of the victims” and saying that “scientific research needs time to get done”. No, the Chinese authorities have not been transparent at all, but it appears that they have been reflexively covering up every possible hypothesis and line of evidence rather than trying to run cover for the Wuhan Institute of Virology in particular (for example).
I find this preprint quite convincing. There are multiple lines of evidence that all point in the same direction, and some of these are things that even the Chinese authorities have not been forthcoming about. At this point, I am going to work on the basis that the Huanan Seafood Wholesale Market was the origin of the coronavirus pandemic. It would take extraordinary and dramatic evidence to convince me otherwise, and I doubt that anything like that is coming.
