Since the pandemic began in 2020, there has been feverish debate about where it began. While we knew early on that the origins could be traced down to the Huanan seafood market in China's Wuhan, several scientists argued that it could have leaked from a lab. Tremendous misinformation, coupled with fear for the virus also gave rise to conspiracy theories such as Covid-19 being a bioweapon. The lab leak theory stuck for a while, but two latest pathbreaking studies have been able to rule it out. While one looked at the location of the first cases in Wuhan, the other analysed the genomes of the first samples found in Wuhan.
The spread of two different lineages of the virus and the geolocations of the first known patients of Covid all point to the Huanan market. "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," the paper said.
In combination, these two studies have thrown significant light on the origins of the pandemic. Here's a look at the key findings.
Early cases all lead to the seafood market
One of the papers — The Huanan Seafood Wholesale Market in Wuhan was the early epicenter of the COVID-19 pandemic — published in Science magazine found that 155 of the 174 earliest known cases of Covid-19 were found near the Huanan market. They used the geolocations of these cases to ascertain that some of them were not vendors, but people who lived in close proximity to the market. The highest density of the first cases was also surrounding the market.
Further investigations revealed that most of the early cases without any links to the market either lived close to it or worked in the area, which meant the virus had started spreading through the vendors of the market to those present in close proximity to the market. Of the first 41 people who were hospitalised with Covid symptoms by January 2020, 66% or 27 of them had also been directly exposed to the seafood market.
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Two different lineages can be traced back to the market
In the paper titled 'The molecular epidemiology of multiple zoonotic origins of SARS-CoV-2', scientists wrote that most Covid cases found before February 2016 likely spread from two lineages of the virus A and B. They analysed the genomic diversity of the early cases and found that the first lineage to appear in humans for lineage B, after which lineage A emerged. "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."
In the other study, researchers found the "center-point of the 11 lineage B cases was 1.95km from the Huanan market". The first known cases infected with lineage A had been in close proximity to the market — one of them resided near it, and showed symptoms even before there was knowledge of a novel virus spreading, and the second person stayed in a hotel near the market before showing symptoms. It concluded, "That both identified lineage A cases had a geographical connection to the market, in combination with the detection of lineage A within the market (24), support the likelihood that during the early epidemic lineage A was, like lineage B, disseminating outward from the Huanan market into the surrounding neighborhoods." This was yet another indicator that pointed to the Huanan market being the origin of the Covid-19 virus.
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It wasn't one event
Researchers said it was likely more than one event that caused the pandemic and not one. It was likely that the Covid virus jumped from animals to humans at least twice. "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." The scientists believe that the virus probably did not circulate within humans before November 2019, and there was a small window of time between when the virus infected humans and when the first Covid cases were reported.
It likely came from live animals
Researchers found that up until November 2019, multiple species of live, wild-captured or farmed mammal species such as red foxes, hog badgers and common raccoon dogs were sold at the Huanan market. These species are known to be animals that host SARS-CoV-2 progenitor viruses. Samples taken from cages, carts and freezers in the southwest corner of the market tested positive for the virus. "This is the same section where vendors were selling live mammals, including raccoon dogs, hog badgers, and red foxes, immediately prior to the COVID-19 pandemic. Multiple positive samples were taken from one stall known to have sold live mammals, and the water drain proximal to this stall, as well as other sewerages and a nearby wildlife stall on the southwest side of the market, tested positive for SARS-CoV-2," the study said.
