Laboratory or market? Some people decided very early on about the possible origin of the corona pandemic. Others expressed strong doubts about it. But even after almost five years, the question has not yet been finally answered. Now a study has come to the conclusion that the virus most likely jumped to humans through the trade in wild animals: through zoonosis.
The scientists evaluated the genetic material of more than 800 samples collected from the Huanan Seafood Market in Wuhan and its surroundings from January 1, 2020. They also analyzed gene sequences from people who were infected with Sars-CoV-2 early in 2020. The results have now been published by the Cell journal.
The data collected indicate that the virus found at the market after it closed on New Year’s Day 2020 has the same ancestor as the pathogen that gave rise to the pandemic. The argument: In all positive samples from a cage system, the researchers were able to detect DNA from wild animals, including species such as civet cats, bamboo rats and raccoon dogs, which had previously been identified as possible intermediate hosts. The authors of the study are therefore strengthened in their assumption that Sars-CoV-2 was brought to Wuhan through the wildlife trade and jumped to humans there.
The other theory is that the virus was passed on to the Huanan Seafood Market by staff at the local high-security laboratory through carelessness or negligence via infected people and was then passed on to other people. The Wuhan Institute of Virology and other research institutions have been conducting research into coronaviruses, partly with the help of US funding. This is considered one of the pieces of evidence for this theory, which was put forward by Australian scientists, among others, in March.
The group from the Kirby Institute at the University of New South Wales came to this conclusion: “The corona pandemic is more likely to have an unnatural origin than a natural one.” This was reported by the journal Risk AnalysisAlthough they did not have any new data at their disposal, they instead re-evaluated all publications known to date using a risk assessment tool: the so-called Grunow-Finke Risk Assessment Tool. However, this was no more conclusive evidence than the analysis now presented.
“The data have the character of strong evidence, but are not conclusive,” says Christian Drosten, director of the Institute of Virology at Berlin’s Charité, about the latest scientific publication. “The reason is that no samples were taken directly from animals, but that swab samples from surfaces were only taken and tested after the market was closed and cleared out. There is always the possibility that the virus found in this way also came from infected people.”
It cannot be ruled out that the coronavirus reached the market in southern China via humans, Drosten told the Science Media Center internet portal. “However, this possibility seems very unlikely due to the reconstruction of the evolutionary history of Sars-CoV-2.” The virus that was detected in some of the most suspect samples is very close to the “reconstructable original diversity” of the pathogen. “In addition, both founding lines of the pandemic were detected on the market, which is best explained by multiple transitions from animals to humans. Only when viewed as a whole with the results of other studies does this picture become very clear.”
Christian Drosten: More and more evidence for the market theory
Drosten’s conclusion: No theory can be formally ruled out. However: “Over time, more and more confirming evidence has been added to the market theory. There is still no scientifically convincing evidence for the laboratory origin theory.” Friedemann Weber, director of the Institute of Virology at the Justus Liebig University in Giessen, also sees more evidence for the market theory. The new data is another clue in this context. “In order to conclusively clarify the zoonotic origin of the pandemic, however, direct virus samples from wild animals and humans taken before and at the time of the first infection events would be required,” says Weber.
His colleague Richard Neher from the University of Basel sees the evidence in a similar way. “The genomic data provide no evidence that animals – apart from humans – at the market were infected with Sars-CoV-2. Most of the viral RNA in the samples probably comes from infected humans.” At the time the market was closed and the first samples were collected, on January 1, 2020, more than a hundred people at the market were probably infected with the pathogen and excreted many more viruses than possibly infected animals. “An accumulation of positive samples at a market stall that sold animals can be explained by both infected humans and infected animals.”
