TL;DR: it’s probably bats.

As is normal during critical times, many rumours or conspiracy theories emerged around the source of the coronavirus:

An older uncle will tell you about the European leaders’ hidden plan to wipe old people since they “live too long”, therefore something must be done about it. Christine Lagarde couldn’t keep the secret and spilled the beans.

Or a well-informed colleague will briefly mention that there is a secret lab near Wuhan and the Chinese have successfully manufactured this human mass biological weapon which was so well designed that it only kills older people.

My mum might say that the Americans are to blame, they must have planted it.

And of course we all should know that Bill Gates already anticipated this disaster back in 2015. Which he actually did, with his now famous TED talk, but so did many scientific studies, some of which we will list below.

The official statement from WHO is as follows:

Coronaviruses are a large family of viruses that are common in animals. Occasionally, people get infected with these viruses which may then spread to other people. For example, SARS-CoV was associated with civet cats and MERS-CoV is transmitted by dromedary camels. Possible animal sources of COVID-19 have not yet been confirmed. 

To be fair, the authorities haven’t done a great job when it comes to transparency, which is one of the reasons of all these theories. Another one is a simple human flaw: our hunger for the sensational and secret.

Supporting Evidence that it’s likely an Animal Source

To test our assumptions, we’ve done a quick query on core.ac.uk using the keywords: sars+coronavirus+reemerging.

This resulted in a plethora of studies on this topic, with a vast majority showing that bats are vast reservoirs for viruses, but also that this animal is linked to emergence of SARS, another type of coronavirus.

Here are some examples:

• A study published by the American Society for Microbiology in 2007 has found a strong connection between the re-emergence of SARS in late 2003 and the re-opening of a wildlife market in southern China:

The small re-emergence of SARS in late 2003 after the resumption of the wildlife market in southern China and the recent discovery of a very similar virus in horseshoe bats, bat SARS-CoV, suggested that SARS can return if conditions are fit for the introduction, mutation, amplification, and transmission of this dangerous virus.

• A 2010 study analysing viruses in a species of bats from Faridpur, Bangladesh found a virus ancestral to the GBV-C virus. GBV-C (also known as Hepatitis G virus (HGV)) has frequently been isolated from humans in many regions of the world, including India and Bangladesh.

• Another study looking at gastrointestinal tissue obtained from bats collected in caves in Nigeria that are frequented by humans, found a new coronavirus, one with a distinctive genomic organization that may provide insights into coronavirus evolution and biology.

• Finally, a study from 2006 shows the first evidence for natural recombination in coronavirus associated with human infection. In a very simplified form, this means that different strains of the virus recombine and bring forth novel strains.

“This high frequency of recombination has resulted in the generation of a high diversity of coronaviruses in different animals. Before the SARS epidemic in 2003, a total of 19 coronaviruses were known, including two human, 13 mammalian and four avian coronaviruses. After the SARS epidemic, within a short period of three years, 20 additional novel coronaviruses were described. These  include  three  human  coronaviruses,  11  mammalian  coronaviruses  and  six  avian coronaviruses. Notably the recent discovery of at least eight different species of coronaviruses in  bats  in  Hong  Kong,  including  SARS-CoV-like  viruses.

The high frequency of 13 recombination in such a high diversity of coronaviruses may easily result in the generation of novel coronavirus species or genotypes that can cross host species barriers, leading to major zoonotic outbreaks with disastrous consequences.”

The Dilemma

One of the problems we’re facing has to do with access to data. On the one side, we have studies suggesting a very simple transmission mechanism. To be fair, this is not forensically accurate – we don’t know the exact bat which had the virus and came in contact with a pangolin or a snake, raccoon dogs, porcupines and deer. But it’s extremely probable. How probable? It’s pretty hard to test because of the moral barriers (you’d need to infect species in a bio system or market) but not impossible.

On the other side, there are the conspiracy theories with nothing as backing. However, these manage to get traction because they refer to ideas used over and over again (e.g. the rich are out there to kill us) in the hope that repetition will make them more credible (see previous post: the validity effect describes how individuals tend to believe information is correct after repeated exposures).

If the opposing theories (scientific versus conspiracy) explaining the emergence of Covid-19 were on a par, if they could explain a phenomenon equally well, we would invoke Occam’s Razor: the best practice in that case would have been to go with the simplest explanation that offers a good enough answer as the testability of more complex theories is low.

But let’s be honest, the two cannot be compared: for the conspiracy theories there is no evidence, while the scientific proposals are backed by numerous peer-reviewed studies. So we cannot grant the #covidiots the honour of applying Occam’s Razor to this debate. And even if we did, they would lose.

We’ll stick to the base tenant of the scoring algorithm in Argumentful: no backing = 0% confidence. Sounds safe, doesn’t it?