The origins of the SARS CoV-2 virus are a highly debated political hot button that has galvanised some very strong rhetoric. The most commonly shared hypothesis is that the virus was spread through a live wild animal in the Huanan Seafood Market in Wuhan, China. The other hypothesis is that the virus was manufactured or discovered and then either leaked into the nearby wet market or intentionally spread by Chinese state actors.
Why Chinese state actors would seek to spread a pandemic by releasing it into their own cities is a question that the latter hypothesis has been unable to answer. As a result, it is generally accepted that the virus began spreading in humans due to either animal to human spillover at the market or because of a leak at the Wuhan Institute of Virology, a biomedical facility famous for its research on all types of coronaviruses.
But now two new preprint studies throw some light on the origins of the virus.
The two separate studies claim that the virus was spread to humans in the Huanan Seafood Wholesale Market and that it was not one or two, but multiple spillover events that caused the virus to spread to the first 174 individuals who were hospitalised.
The scientists behind the ‘The Huanan market was the epicenter of SARS-CoV-2 emergence’ used data from the World Health Organisation fact-finding mission to determine the origin of the SARS CoV-2.
“We used the maps in the WHO mission's report on the origin of SARS-CoV-2 to extract latitude and longitude for most of the known COVID-19 cases from Wuhan with symptom onset in December 2019,” said Michael Worobey, lead author of the study and the Professor and Head of Ecology and Evolutionary Biology at the University of Arizona, on Twitter.
We used the maps in the WHO mission's report on the origin of SARS-CoV-2 to extract latitude and longitude for most of the known COVID-19 cases from Wuhan with symptom onset in December 2019. pic.twitter.com/8u5OSnd7xk
— Michael Worobey (@MichaelWorobey) February 26, 2022
The scientists behind the study claim that the virus was spread from the market due to the geographical proximity of the first reported infections to the market itself. Also pointing towards this conclusion is the fact that several thousand specimens of various species of wild animals were being sold in the market. These animals were sourced from far-flung areas of the continent from remote jungles, and biomes, potentially carrying the virus on them.
Unlike most other wet markets in the country, the Huanan Seafood market had vendors selling species like raccoon dogs, Amur hedgehogs, Siberian weasels, hog badgers, Asian badgers, Chinese hares, Pallas's squirrels, masked palm civets, Chinese bamboo rats, Malayan porcupines, coypus, marmots, red foxes, minks, red squirrels, wild boars and complex-toothed flying squirrels.
But the theory is not without its counterpoints. While the Chinese Centre for Disease Control and Prevention had found several environmental samples of the virus in the market, the organisation had stated that the market was not the origin for the virus as animal samples had not tested positive. Molecular clock studies that suggest the index case was infected in mid-October or early November also broaden the horizon of potential spillover points.
But it does support the same thoughts as the report published last year in The Lancet Journal, where two dozen biologists, ecologists, epidemiologists, physicians, public health experts and veterinarians stated that there was no scientific evidence of the virus was leaked from a lab in China.
The study ‘SARS-CoV-2 emergence very likely resulted from at least two zoonotic events’ at the same time suggests that the virus that jumped from animals to humans not only occurred more than twice but also from different lineages. Scientists found that there were two lineages of SARS CoV-2 during the start of the pandemic.
“Background info: there were two lineages of SC2 at the beginning of the pandemic: A and B,” stated Jonathan Pekar, the lead study of the author on Twitter.
We released 2 preprints on the origin of SARS-CoV-2 (SC2) over the weekend. Long 🧵👇
1. SARS-CoV-2 emergence very likely resulted from at least two zoonotic eventshttps://t.co/nMpj0Q5Z1A1/— Jonathan Pekar (@jepekar) March 4, 2022
Lineage A appeared to be older lineage and descended from bat coronaviruses, while the B lineage had a genetically distant relation to bat coronaviruses. Despite this, it was lineage B that was found predominantly in those infected around the Huanan market. From further studies, the scientists behind the paper were able to determine that since Lineages A and B were not each other’s ancestors, there must have been multiple introduction events to the human population which resulted in the birth of the COVID-19 pandemic as we know it today.
The results also hold more water since other coronaviruses like SARS CoV-1, which causes the Severe Acute Respiratory Syndrome (SARS), and the MERS CoV, which causes Middle East Respiratory Syndrome (MERS), also had multiple introduction points.
But while these two studies throw more light on the issues, they are constrained by factors like time and access. The COVID-19 pandemic emerged over two years ago, and finding primary data is problematic.
“I think what they’re arguing could be true,” Jesse Bloom, a Fred Hutchinson Cancer Research Center virologist, told the New York Times. “But I don’t think the quality of the data is sufficient to say that any of these scenarios are true with confidence.”
