Asian Wet Market - Credit Wikipedia
#16,904
The debate over the origins of the SARS-CoV-2 virus - whether it is the result of a zoonotic spillover event, or, as some contend, the product of a lab experiment/escape - remains a hot button topic both in scientific circles, and on the internet.
Having written extensively on the risks of GOF (Gain of Function) experiments, and actual lab escapes (see here, here, here, here, here, and here), the lab accident theory certainly seemed plausible.
Add in China's slow-rolling of information, and their stonewalling of International investigations, and it only added fuel to the fire. But at the same time, solid evidence of a lab leak has been lacking.
The alternate theory, that COVID was the result of an animal spillover at the Wuhan Market has simplicity in its favor, and closely aligns with our understanding of how SARS-CoV emerged in 2002, and spillovers of avian influenza into the human population in Asia (see The Lancet: Poultry Market Closure Effect On H7N9 Transmission).
And frankly, I've been writing about the dangers of zoonotic spillover from wet markets since this blog started in 2006 (see here, here, here). Factor in that several new `SARS-like' viruses have been detected in the wild (see PNAS: SARS-like WIV1-CoV Poised For Human Emergence) since 2003, and a spillover makes sense.
In fact, six weeks before the Wuhan outbreak began, in African Swine Fever's (ASF) Other Impacts; Pharmaceuticals, Bushmeat, and Food Insecurity, I even speculated that China's ASF outbreak could lead to increased `bushmeat' consumption, which in turn might spark another SARS-like outbreak.While I've leaned towards COVID being the result of a natural spillover, I've considered the lab leak theory a possibility. But what we've needed is evidence, and without that, I've remained on sidelines of this contentious debate.
Yesterday the journal Science published evidence gathered by Michael Worobey et al. and Jonathan Pekar et al. that strongly suggests a Wuhan Market origin for SARS-CoV-2.
While I doubt this is going to satisfy everyone, the evidence they present is pretty compelling. You'll find the press release, and links (and abstracts) to both papers below. I'll have a brief postscript after the break.
NEWS RELEASE 26-JUL-2022
Studies point to Huanan market as epicenter of SARS-CoV-2 emergence, from activities associated with wildlife trade
**COVID Immediate Release**Peer-Reviewed Publication
AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)
Two studies published in Science by Michael Worobey et al. and Jonathan Pekar et al. use complementary approaches – involving spatial and environmental analyses, as well as molecular analyses – to provide evidence that the Huanan market in Wuhan, China, was the early epicenter for the COVID-19 pandemic. The scientists concluded that SARS-CoV-2 was very likely present in live mammals sold at this market in late 2019 and suggest the virus spilled over into people working or shopping there from two separate zoonotic transmissions, in which lineage A and B progenitor viruses were both circulating in non-human mammals prior to their introduction into humans. Future work, say the authors of both studies, should be focused on better understanding events upstream of the introduction of SARS-CoV-2 to the market, including where the wild mammals for sale at Huanan came from, to lower the risk of future pandemics.
Despite the observation that the preponderance of earliest known COVID-19 cases – flagged by hospitals in Wuhan in December 2019 – were linked to the Huanan market, this did not establish activities at the Huanan market as the trigger for the pandemic. But, as Worobey and colleagues note, determining the epicenter of the COVID-19 pandemic at the neighborhood- rather than city-level could help resolve if SARS-CoV-2 had a zoonotic origin. To test the hypothesis of the market as the pandemic’s epicenter, Worobey et al. obtained data from a range of sources. First, they used mapping tools to estimate the longitude and latitude locations of more than 150 of the earliest reported virus cases from December 2019, including those without reported direct links to the market. The highest density of these cases centered around the Huanan market, they say. By mapping cases from January and February of 2020 using data from Weibo, a social media app that created a channel for people with Covid to seek medical help, the researchers identified cases in other parts of central Wuhan radiating from the market as the pandemic progressed. Using social media "check-in" data, the researchers performed analyses to rule out the many other locations in Wuhan, a city of 11 million, that would have been equally or more likely than the market to sustain the first cluster of a new respiratory pathogen. In further analyses, they report that multiple plausible intermediate wildlife hosts of SARS-CoV-2 progenitor viruses were sold live at the Huanan market until at least November of 2019. Using and extending a data set on samples from surfaces in the Huanan market, they identified five stalls that were likely selling live or freshly butchered mammals; the proximity to such live mammal vendors was predictive of human virus cases, their analyses show.
To further understand the circumstances that led to the pandemic's origin, Pekar and colleagues analyzed the genomic diversity of SARS-CoV-2 early in the pandemic. While the diversity of SARS-CoV-2 increased as the pandemic spread from China to other countries, two lineages of SARS-CoV-2 – designated A and B – marked the beginning of the COVID-19 pandemic in Wuhan. Only lineage B was represented in the eleven sequenced genomes from humans directly associated with the Huanan market. The earliest lineage A genomes from humans lacked any known contact to the market but were sampled from humans who lived or stayed close by. It has been hypothesized that the two lineages emerged separately. To test this hypothesis, Pekar and colleagues analyzed genomic and epidemiological data from early in the COVID-19 pandemic with models and simulations. Through their analyses, they provide support for two separate introductions of lineages A and B into humans, both circulating in non-human mammals prior, with lineage B first appearing in humans no earlier than late October 2019 and likely in mid-November 2019 and lineage A being introduced within days to weeks of this event. Their simulations do not support a single introduction of the virus giving rise to the observed patterns of virus lineage spread. Further, the results from the study of Worobey et al., they say, are consistent with the idea of a separate and subsequent origin of lineage A at the Huanan market in late-November 2019. These findings, say the authors, indicate that it is unlikely that SARS-CoV-2 circulated widely in humans prior to November 2019 and define the narrow window between when SARS-CoV-2 first jumped into humans and when the first cases of COVID-19 were reported. The authors report several limitations to their studies, in both cases.
***A related news briefing was held as a Zoom Webinar on 26 June 2022, at 2:00 p.m. U.S. ET. Recordings of the briefing can be found here.
JOURNAL
Science
DOI 10.1126/science.abp8715
MICHAEL WOROBEY JOSHUA I. LEVY , LORENA MALPICA SERRANO , ALEXANDER CRITS-CHRISTOPH, JONATHAN E. PEKAR , STEPHEN A. GOLDSTEIN , ANGELA L. RASMUSSENSCIENCE26 Jul 2022First Release
Abstract
Understanding how severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in 2019 is critical to preventing zoonotic outbreaks before they become the next pandemic. The Huanan Seafood Wholesale Market in Wuhan, China, was identified as a likely source of cases in early reports but later this conclusion became controversial. We show the earliest known COVID-19 cases from December 2019, including those without reported direct links, were geographically centered on this market. We report that live SARS-CoV-2 susceptible mammals were sold at the market in late 2019 and, within the market, SARS-CoV-2-positive environmental samples were spatially associated with vendors selling live mammals. While there is insufficient evidence to define upstream events, and exact circumstances remain obscure, our analyses indicate that the emergence of SARS-CoV-2 occurred via the live wildlife trade in China, and show that the Huanan market was the epicenter of the COVID-19 pandemic.
JONATHAN E. PEKAR ANDREW MAGEE EDYTH PARKER NIEMA MOSHIRI KATHERINE IZHIKEVICHJENNIFER L. HAVENSKARTHIK GANGAVARAPU LORENA MARIANA MALPICA SERRANO ALEXANDER CRITS-CHRISTOPH[...]JOEL O. WERTHEIM +20 authors Authors Info & AffiliationsSCIENCE26 Jul 2022First Release
AbstractUnderstanding the circumstances that lead to pandemics is important for their prevention. Here, we analyze the genomic diversity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) early in the coronavirus disease 2019 (COVID-19) pandemic. We show that SARS-CoV-2 genomic diversity before February 2020 likely comprised only two distinct viral lineages, denoted A and B. Phylodynamic rooting methods, coupled with epidemic simulations, reveal that these lineages were the result of at least two separate cross-species transmission events into humans. The first zoonotic transmission likely involved lineage B viruses around 18 November 2019 (23 October–8 December), while the separate introduction of lineage A likely occurred within weeks of this event. These findings indicate that it is unlikely that SARS-CoV-2 circulated widely in humans prior to November 2019 and define the narrow window between when SARS-CoV-2 first jumped into humans and when the first cases of COVID-19 were reported. As with other coronaviruses, SARS-CoV-2 emergence likely resulted from multiple zoonotic events.
While there are still admittedly gaps in our understanding of what occurred in Wuhan, China in Nov-Dec 2019 - including the lack of an identifiable intermediate host animal for the virus at the market or in its supply chain - the evidence we currently have strongly suggests the Wuhan market is the source of this outbreak.
But nothing is written in stone.
