EXPLAINER

Where did the coronavirus come from?

A Wuhan market security guard at the start of the pandemic. Picture: Shutterstock
A Wuhan market security guard at the start of the pandemic. Picture: Shutterstock

It would be nice to think that identifying the source of the epidemic which has ravaged the planet would be solely about the science - but it's not: politics has intruded.

Some things we know without controversy. The first case of COVID-19 was identified on December 8, 2019 in the city of Wuhan in China. That is not in dispute, though there may have been earlier cases which weren't spotted.

But there is a laboratory in Wuhan - the Wuhan Institute of Virology - and some have speculated scientists there were working on the virus which then leaked, and once out, it spread like a bushfire.

A former director of the respected Centres for Disease Control and Prevention in the United States, Dr Robert Redfield, said: "I am of the point of view that I still think the most likely etiology of this pathogen in Wuhan was from a laboratory, escaped. The other people don't believe that. That's fine. Science will eventually figure it out."

He accepted that he had no conclusive evidence. It is his opinion, albeit as an expert in the way viruses originate and spread.

So it was the lab?

Not so fast.

The more general expert view remains that the origin was not the laboratory.

Professor Adrian Esterman of the University of South Australia told this paper that the most likely source was an animal.

"The most likely scenario, is that the virus is hosted by horseshoe bats," he said, "which have then transferred it (for example, via droppings) to another mammalian species (for example, pangolins), which have then passed it on to humans.

"However, this is all speculative," the epidemiologist said.

Pangolins have scales so they look like reptiles but they are, in fact, mammals. Their scales are used in traditional medicine. The animal is considered a delicacy in China and Vietnam.

The virus certainly spread from a crowded fresh food market in Wuhan, but how it got there is not known.

On Professor Esterman's favoured scenario, the virus originated in bats and was then transferred to pangolins and then to humans. One possibility is that each species, including humans, caught the virus by some sort of indirect contact, perhaps though the droppings of a carrier.

Definitely China, though?

Again, not quite so fast.

Prof Esterman pointed to an interesting piece of research. According to the highly-respected Naturejournal, the coronavirus was found in horseshoe bats which were killed in 2010 and kept in a freezer.

To spell it out: the dead bats with the coronavirus were killed way before the current epidemic took off and they were found outside China. While China was probably the source of the current epidemic, it may not have been the source of the virus itself.

And the animal-to-human route was very likely - but not definite.

As the Nature scientific journal put it: "Strong evidence suggests that SARS-CoV-2 originated in horseshoe bats, but whether it passed directly from bats to people, or through an intermediate host, remains a mystery."

So much for the science

Politics has intruded.

Former US President Donald Trump was very keen to call the virus a Chinese virus. He referred to "Kung Flu" in a rally. China was keen for it not be seen as a Chinese virus. The result was the search for the source of the epidemic became politicised, including by the federal government in Canberra.

Echoing then-president Trump, Australia's Prime Minister Scott Morrison called for an international inquiry. China retaliated with crippling tariffs on Australian wine and barley.

When the atmosphere cooled somewhat, the World Health Organisation sent an international team of scientists to Wuhan.

The WHO report (which was written by the outside scientists alongside Chinese scientists) was couched in possibilities and likelihoods.

It said a direct spillover from animals to humans was "a possible-to-likely pathway" and a route through an intermediate animal (like bats to pangolins to humans) was a "likely-to-very likely pathway". In other words, they discounted the idea it came out of the Wuhan lab.

But the WHO's own head then cast doubt on the WHO report.

The organisation's director-general, Tedros Adhanom Ghebreyesus, said the investigation left important questions unanswered and "all hypotheses remain on the table". He added the WHO needed "full access to data".

More than a dozen countries, including Australia, said the report "lacks crucial data". China denied that.

So, what's most likely?

An Australian scientist who was in the WHO investigative team pointed to the market in Wuhan.

"We talked to our Chinese counterparts - scientists, epidemiologists, doctors - over the four weeks the WHO mission was in China," said Prof Dominic Dwyer, a microbiologist at the University of Sydney.

"We were in meetings with them for up to 15 hours a day, so we became colleagues, even friends. This allowed us to build respect and trust in a way you couldn't necessarily do via Zoom or email.

"Our investigations concluded the virus was most likely of animal origin. It probably crossed over to humans from bats, via an as-yet-unknown intermediary animal, at an unknown location."

The market may have been just the super-spreader venue. "The market in Wuhan, in the end, was more of an amplifying event rather than necessarily a true ground zero. So we need to look elsewhere for the viral origins."

A conclusion - and some hope

The lab was thought to be unlikely as the original source but not completely ruled out. The market in Wuhan was clearly a big spreader of the virus.

What is not in doubt is that, wherever it originated, it is out and seemingly unstoppable.

It mutates to stay a step ahead of the scientists.

But there is hope, Prof Esterman said.

"A number of research groups are now working on a vaccine against all coronaviruses, so that mutations simply won't matter.

"This would be a game-changer, and is a good possibility."

This story Where did the coronavirus come from? first appeared on The Canberra Times.

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