The existence of a coronavirus related to severe acute respiratory syndrome coronavirus (SARS-CoV) was first hinted at by a researcher from the Wuhan University School of Medicine. A coronavirus pathogen was confirmed a week later, and its genetic sequence made public days after that. It was later called SARS-CoV-2.
Fast forward four months.
President Trump continues to present a narrative of lab release; however, the scientific consensus is that SARS-CoV-2 is the result of a natural event during which a bat virus jumped to a human, possibly via an intermediate animal.
The reality is that we still don’t have enough evidence to write an origin story for the cause of coronavirus disease 2019 (COVID-19).
Manufactured or manipulated: a great old movie script
The idea that SARS-CoV-2 is a manufactured virus is titillating but less likely than other origin stories.
Experts in viral genetics and emerging viruses have already described the likely path for SARS-CoV-2; one of stepwise evolution consistent with patterns frequently seen among other coronaviruses in recent history. The manipulation of a bat coronavirus or its synthetic creation would need a very high level of coronavirus and molecular virology expertise, not just to construct it, but to cover the tracks of that construction.
Experts in the field have described an evolutionary pattern to the genetic differences and motifs which distinguish SARS-CoV-2 from any other known coronavirus.
Nefarious agents would also need access to specialised reagents and equipment. This is not impossible but is unlikely. The US intelligence community concurs with the scientific consensus; that SARS-CoV-2 is unlikely to have been genetically modified or created in a lab.
Laboratory study of a wild virus gone wrong?
There is no evidence that scientists anywhere were previously working with SARS-CoV-2, merely allegation. But if SARS-CoV-2 did escape a lab, the story goes, it may have hitched a ride in an infected lab animal or researcher. Biosecurity procedures must have failed for this to occur; something not unheard of. Once in the wild, the concern is that virus spread among animals or humans and travelled worldwide from there. Another obvious problem with this version is that the virus could also have happened naturally, without this convoluted lab intermediary process.
Nature as the source, humans as facilitators of the meeting
Over 60% of new or emerging infectious disease in humans originate from animals; they are zoonoses. Humans have a long and varied history of acquiring zoonoses. We know that influenza A viruses – the “usual” cause of human pandemics – are bird viruses that spread to many other mammals, often when those animals are kept close together. The 1918 human influenza pandemic virus shares features with avian viruses while the 2009 pandemic had evolutionary help from pigs. The Ebola epidemic in west Africa in 2014-16 that caused unprecedented levels of infection and death was suspected of starting when a human was infected by a bat.
SARS-CoV-2 is the seventh coronavirus known to cause human disease and the third linked to bats within 20 years. There is precedent supporting the natural origin of SARS-CoV-2 as a zoonosis. Scientists have traced the origins of different endemic human coronaviruses (229E, OC43, NL63, HKU1) from bats through rodents, cows or camels, now perhaps pangolins, to humans. In the 2002-04 SARS epidemic, the causative SARS-CoV originated from a bat coronavirus that likely passed through either palm civets or racoon dogs. For MERS-CoV, the journey was probably from bat to camel to human. Both viruses relied on humans bringing farmed or exotic animals, each with their own large but poorly studied viral populations, into close proximity to other animals and to us.
Vector-borne zoonoses due to Ross River virus and Zika virus occurred after interactions between an animal reservoir, a mosquito vector and us. We make these interactions more likely by encroaching on habitats, recreating suitable habitats near us, or through climate change.
We don’t have evidence, but we do have precedent
Scientists have allowed for the possibility that new evidence may uncover facts supporting a different origin story. There is no direct evidence to support the lab escape or modification narrative any more, or less, than the evolutionary hopscotch story. But we do have circumstantial evidence for natural evolution: a very closely related horseshoe bat coronavirus – still likely separated by hundreds of genetic differences equating with decades of evolutionary difference; pangolin coronaviruses that are generally more distinct but have contributed some key genetic sequence; millions of potential exposures annually to bat coronaviruses; a broad, varied and unexplored constellation of bat coronaviruses; a well-known pattern of intermingling and mutation among coronaviruses and a lot of precedents. The circumstantial evidence suggests SARS-CoV-2 has originated from humans and animals once again being brought into close contact. Experts aren’t surprised SARS-CoV-2 has emerged as yet another zoonosis.
We also shouldn’t overlook the politicisation of this topic, the desire to apportion blame and the lack of expertise among sources preferring a more exciting, but poorly supported narrative. Underpinning a tale of natural evolution is the knowledge that human habits, once again, created conditions for and perpetuated the spread of a new infectious pathogen.
This won’t be our last dealing with a newly emerged coronavirus. Hopefully, in the future, better-funded research science will have prepared answers for the public and our leaders to address the complex scientific concepts we’re struggling to come to terms with during COVID-19.
- A pangolin in defensive posture, Horniman Museum, London.
Author: Stephen Dickson
- First posted 04MAY2020, 5:30pm