How did coronavirus start and where did it come from?

 

Image by Tumisu from Pixabay

In the public mind, the story of the origin of the coronavirus seems to be well-established: by the end of 2019 someone in the Huanan marine fish market now famous in Wuhan became infected with an animal virus.

Everything else is part of the worst-case scenario, Covid-19 has spread from that first cluster in the Chinese capital of Hubei to the plague that has killed an estimated 211,000 people so far.

Stock photos of pangolin - an anteater-like mammal - have reached the news bulletins, suggesting that the animal was a breeding ground for the virus before it spread to humans.

But there is uncertainty about certain aspects of the Covid-19 origin story that scientists are trying so hard to unravel, including what genes have been transmitted to man. They try hard because knowing how the epidemic starts is key to the next stop. 

Prof Stephen Turner, head of the department of microbiology at Melbourne’s Monash University, says it is very likely that the virus originated in bats.

But that's where his end ends, he says.

On the assumption that the virus originated in Wuhan's live animal market from the interaction between animal and human, Turner states: "I don't think it ends with anything."

"Part of the problem is that the details are the same," he said, adding that germs of this type are constantly circulating in the animal kingdom.

The fact that the virus has infected a tiger at a zoo in New York shows how the virus can travel among species of animals, he said. "Understanding the range of species this virus can infect is important as it helps us reduce where it is likely to occur."

Scientists say that the virus is more likely to be transmitted to bats but that it first passed through a human communicator just like any other coronavirus - the 2002 Sars outbreak - from horseshoe bats to cat-like civets before infecting humans.

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One animal that is considered a link between bats and humans is the pangolin. The International Union for Conservation of Nature states that they are “the world's smallest mammal” and are known for their flesh and for their alleged health risks.

As reported in Nature, penguins were not listed on Wuhan's merchandise, although these omissions may be intentional as it is illegal to sell them.

"Whether the poor pangolin was the species in which it jumped, is unclear," Turner said. "Mixed into something else, mixed with poor pangolin, or jumped into people and came from people."

Professor Edward Holmes, of the University of Sydney, was a fictional researcher in the field of environmental research who examined the possible origins of the virus by looking at its genes. In social media, he stressed that the identity of the species that served as the central manager of the virus is "still uncertain".

Some mathematical studies point to a viral feature that has already emerged in order to attach to human cells. Pangolin were able to develop this feature, but so did cats, buffalo, cattle, goats, sheep and pigeons.

One study claimed that it rejected pangolins as a whole host, because samples of the same bacteria taken from pangolins lacked the amino acid sequence that is seen in the virus that is now circulating in humans.

The research that Holmes has worked on has suggested that the situation in which a person at the Wuhan market encountered an infected animal was the only possible version of the original Covid-19 story. Another possibility is that the generation of the virus is highly contagious and spreads from person to person.

"Once identified, these changes will enable the epidemic to emerge and produce a large number of cases to initiate a monitoring program that has been identified," the study said.

An analysis of the first 41 Covid-19 patients in the medical journal Lancet found that 27 of them were directly exposed to the Wuhan market. But a similar analysis found that the first known case of illness did not.

This could be another reason for doubting the fabricated story.

Prof Stanley Perlman, a leading pathologist at the University of Iowa and a specialist in animal-borne coronavirus outbreaks, says the idea that the link to the Wuhan market coincided simply "could not be closed" but that opportunity "seemed small" because genetic findings had been made locally. of the market.

Perlman told the Guardian Australia that he believed there was a link animal but added that although pangolins are likely to run in the election, "they do not appear to be the main mediator".

“I suspect that any [viral] outbreak occurs in the middle animal if it were. There were no major mutations in the virus during the three months of the epidemic, indicating that the virus is common in humans. ”

The so-called wet markets - where live animals are sold - have contributed to previous outbreaks of coronaviruses, particularly Sars.

Dr Michelle Baker, a CSIRO pathologist who specializes in batches of viruses, says that further research into the origins of Covid-19 has been based on what has been known for some time.

But "we don't really know" how accurate the original story is, he says: "There was some contact [with the Wuhan market] and there were people exposed to the market who were infected."

Baker says the “most likely” is that the virus originated in the bat. “It is a possibility but we will never know. The market was cleaned up very quickly. We can only imagine. ”

"These wet markets have been identified as a problem because you have a variety of interactions," he said. "It's an opportunity to highlight their dangers and an opportunity to put pressure on them."

Turner adds: "We have found the ancestors of the virus, but having more information about the coronavirus in some species may give us an idea of ​​how this material came about and how it came to be."