The rest is part of a horrible story still in the making, Covid-19 extending from this first cluster in the capital of Hubei province in China to a pandemic that has killed around 80,000 people so far.
Archival footage of pangolins – a scaly mammal that looks like an anteater – has reached news reports, suggesting that this animal was the relay of the virus before it spread to humans.
But there is uncertainty about several aspects of the history of the origin of Covid-19 that scientists are working to unravel, including the species that have transmitted it to humans. They’re trying hard because knowing how a pandemic starts is key to stopping the next one.
Professor Stephen Turner, head of the microbiology department at Monash University in Melbourne, says the most likely is that the virus comes from bats.
But that’s where his certainty ends, he says.
Assuming that the virus emerged in the Wuhan live animal market from an interaction between an animal and a human, Turner said, “I don’t think it’s conclusive in any way. “
“Part of the problem is that the information is only as good as the surveillance,” he said, adding that viruses of this type circulate all the time in the animal kingdom.
The fact that the virus infected a tiger in a New York zoo shows how viruses can move between species, he says. “It is important to understand the extent of the species that this virus can infect because it helps us to pinpoint where it might have come from.”
Scientists say it is very likely that the virus originated from bats, but first crossed an intermediate animal in the same way as another coronavirus – the Sars epidemic in 2002 – has passed horseshoe bats to civets looking like cats before infecting humans.
One animal involved as an intermediate host between bats and humans is the pangolin. The International Union for Conservation of Nature claims that they are “the most illegally traded mammal in the world” and are valued for their meat and the claimed medicinal properties of their scales.
As noted in Nature, pangolins were not listed in the inventory of items sold in Wuhan, although this omission may be deliberate as it is illegal to sell them.
“Whether poor pangolin was the species he jumped at is unclear,” said Turner. “It is mixed with something else, mixed with a poor pangolin, or it jumped in people and evolved in people. “
Professor Edward Holmes of the University of Sydney was the co-author of a nature study that examined the likely origins of the virus by examining its genome. On social media, he stressed that the identity of the species that served as an intermediate host for the virus is “still uncertain“.
A statistical study examined a characteristic of the virus that has evolved to allow it to cling to human cells. Pangolins were able to develop this characteristic, just like cats, buffaloes, cattle, goats, sheep and pigeons.
Another study claimed to have excluded pangolins as an intermediary because similar virus samples taken from pangolins lacked a chain of amino acids found in the virus now circulating in humans.
The study Holmes worked on suggested that the scenario in which a human at the Wuhan market interacted with an animal carrying the virus was only a potential version of the original Covid-19 story. Another was the possibility that a descendant of the virus would jump into humans and then adapt as it spreads from human to human.
“Once acquired, these adaptations would allow the pandemic to take off and produce a large enough group of cases to trigger the surveillance system that detected it,” the study found.
Analysis of the first 41 Covid-19 patients in the medical journal The Lancet revealed that 27 of them were directly exposed to the Wuhan market. But the same analysis found that the first known case of the disease was not.
This could be another reason to doubt established history.
Professor Stanley Perlman, a leading immunologist at the University of Iowa and expert on previous animal coronavirus outbreaks, says the idea that the link to the Wuhan market is a coincidence “cannot be excluded “but this possibility” seems less likely “because the genetic material of the virus had been found on the market.
Perlman told Guardian Australia that he believed there was an intermediary animal, but added that although pangolins are possible candidates, they “have not been proven to be the key intermediary.”
“I suspect that any evolution [of the virus] happened in the middle animal if there was one. There has been no substantial change in the virus during the three months of the pandemic, indicating that the virus is well adapted to humans. “
So-called wet markets – where live animals are traded – have been implicated in previous epidemics of coronavirus, especially Sars.
Dr. Michelle Baker, a CSIRO immunologist who studies viruses in bats, says that some of the research into the origins of Covid-19 has strayed from what was known in the past.
But “we really don’t know” how precise the original story is, she said, “There is some kind of connection [to the Wuhan market] and there were people exposed to the market who were infected. “
Baker says that what is “very likely” is that the virus originated in a bat. “It is a likely scenario but we will never know. The market was cleaned up fairly quickly. We can only speculate. “
“These wet markets have been identified as a problem because some species interact,” she says. “This is an opportunity to highlight and repress their dangers. “
Turner adds: “We have found the ancestors of the virus, but having a broader knowledge of the coronavirus in other species could give us a clue to the evolution of this thing and how it jumped. “
- Due to the unprecedented and continuing nature of the coronavirus epidemic, this article is updated regularly to ensure that it reflects the current situation as of the date of publication. All major corrections to this version or to previous versions of the article will continue to be noted in accordance with Guardian editorial policy.