WHO’s whodunnit

World Health Organization (WHO) officials announced their much-anticipated findings on the origins of COVID-19 at a press conference last Tuesday.

The most contentious part of their work has centred around what’s now been labelled the “extremely unlikely” theory that COVID-19 leaked from a Wuhan lab.

Given that this origin story has developed a sizeable fan base amongst conspiracy theorists and COVID sceptics, it’s important to view the announcement through that ever-constant antidote to intrigue and mendacity: science.

The WHO panel reported on four hypotheses that could explain the origin of the COVID-19 outbreak. Lead investigator Peter Ben Embarek listed these as:

1. A direct zoonotic spillover (ie the virus jumped from one animal into the human population)
2. Transmission through an intermediary species
3. Via the food chain (ie frozen food taking the role of transmission)
4. A Wuhan lab-related incident

Hypotheses 1 and 3 were considered possible, however there wasn’t enough evidence to prove a direct jump of the virus from bats to humans or the virus being spread via food processing plants. That could change. Hypothesis 2 – transmission through an intermediary species – was identified as the most likely. A lab-related incident was considered least likely and as such, said Embarek, should not be included in future investigations.

This isn’t the first time that scientists have had to work hard to combat popularly held beliefs that, once circulated via the internet, prove difficult to dispel.

During the press conference, reporter Tom Cheshire, from Sky News Asia asked: “Of the four hypotheses the only one you decisively rejected was the laboratory instance. Could you explain the evidence or the reasoning for discarding that hypothesis?”

Embarek explained that accidental virus releases are “extremely rare” and that, after analysis of the Wuhan lab’s operating procedures, that it would be “extremely unlikely” for COVID-19 to have leaked from there. His conclusion was drawn from two main points:

1. There is no evidence that the virus was studied in any lab before December 2019, and
2. the likelihood that any virus could escape the Wuhan lab was very low.

In other words, Embarek is saying that shadow in the corner of your bedroom could be a tiger but you’d first have to prove the existence of tigers in your area and then the likelihood that one could enter your room without you knowing about it.

However, a rogue tiger roaming the suburbs and sneaking into your room in the middle of the night is the most interesting explanation, right? If COVID-19 was developed and leaked from a lab then that would be the most exciting origin story!

But given that Embarek claims there is no evidence the virus was known to the scientific community before December 2019, that leaves the possibility it was concocted by a Wuhan lab in secret. To debunk that scenario we can look to peer-reviewed studies.

Within the past 10 years researchers have found other coronaviruses with remarkable similarities to COVID-19. In 2013 a coronavirus was discovered in China that has turned out to be 96% identical to COVID-19. While that sounds like a lot, that 4% difference counts for a lot. Don’t be tempted to think of genetic similarity like a grade for uni. Handing in a chimp when asked for a human will not give you a High Distinction. The human genome is 60% identical to both bananas and chickens, so passing off either as a person should not be given a passing grade.

But could this 2013 coronavirus have evolved into COVID-19? No. The 96% genetic similarity between both viruses indicates a common ancestor rather than a direct descendent, much as chimps and humans have both evolved from a common ancestor. But since the genomes are so close could it possible for a lab to genetically engineer one into the other? Not likely.

American researchers published evidence against this scenario in February 2020. They reported that for any lab to make a virus with current technology, an existing virus would most likely be used to make “logical or targeted changes” to a genetic sequence. This would have left a genetic signature in the COVID-19 genome, much like plagiarising a sentence of someone else’s work in your essay. It might not seem like much a good database could find you out! COVID-19 has no such genetic signatures.

There have been some researchers who have published work that a lab origin for COVID-19 is not impossible. They argue that an innovative combination of genetic engineering techniques could have created COVID-19 without any telltale signatures. However their theory is still far less likely than the virus having developed naturally in the wild – we could have made a hinny in a lab, but it’s more likely a horse and a mule got busy one moonlit night.  Scientific consensus has the most likely scenario that COVID-19 developed in bats and then jumped to another species. During that jump the virus went through rapid evolutional change that allowed it to make another jump to humans. It’s also what the WHO has concluded to be the most likely scenario.

It’s the same origin story that was posited last year and is still the best scenario for future research. While there are other more interesting origin stories out there when it comes to the health and safety of the world’s population, science should decide which story gets the green light.