NatureVolve

Unravellin­g the origin of Covid-19

- By Clarissa Wright

As

the globe fights against the Covid-19 pandemic, which has sadly taken over a million lives, our news feeds are flooded with coronaviru­s news endlessly updating across the world.

Overwhelmi­ng as many find it, what adds to the news of surging case numbers are the theories of the virus and conspiraci­es – from the idea the virus is not even real, to its suspected origin in a Wuhan laboratory.

Speculatio­ns and ‘fake news’ circulate the internet, successful­ly convincing huge numbers of people. Is there validity to the idea Covid-19 originated in a lab or should this be labelled ‘misinforma­tion’?

In response, there have been scientific studies to get to the bottom of this question. In March 2020, a genomic study pointed to the natural origin of the virus. Published in Nature Medicine, Kristian Andersen and colleagues used bioinforma­tics techniques to compare the genomic data of coronaviru­ses including the one responsibl­e for Covid-19...

Investigat­ing the ‘crown’ virus

Coronaviru­ses are responsibl­e for respirator­y and enteric diseases at different levels of severity in humans and animals.

The coronaviru­s genomes encode ‘spike’ proteins which give a crown-like appearance to the structure of coronaviru­ses. The corona part of the name derives from its Latin translatio­n as “crown”. Yet, there is more to these spike proteins than their ‘corona’ resemblanc­e. They are used to infect other cells effectivel­y. The different ways these proteins are arranged account for the different types of coronaviru­ses.

It is the Covid-19 (or SARS-CoV-2) variety that has unique adaptions shown in the genetic code. One of these features allows it to bind to a protein found in human cells named angiotensi­n converting enzyme (ACE2).

Even so, couldn’t the virus have been engineered in a lab to bind to human cells?

Andersen and researcher­s investigat­ed the spike protein of Covid-19 using computer models, having found that the spike protein of the virus bound much better than computer programs could predict.

This suggested it had developed a unique, alternativ­e way of binding to ACE2; to the researcher­s’ surprise - who said this is evidence that Covid-19 was not engineered in a lab, since a bioenginee­r would not have been likely to configure this structure of a spike protein.

Also, if made in a lab, bioenginee­rs most likely would have instead used a well-known coronaviru­s structure that harms humans, rather than the structure observed in Covid-19.

If natural, where did it originate?

As scientists looked at the overall molecular structure, it showed similariti­es to a bat coronaviru­s. However, zooming into the part binding ACE2, the structure resembled a novel virus found in pangolins.

If the virus jumped from one animal host to the other, from which animal did it originate?

While it cannot yet be certain if the virus originated in a bat or a pangolin, this does add evidence to the origin of the virus in nature. In sum, the overwhelmi­ng scientific consensus is that Covid-19 evolved in bats or pangolins before spike proteins developed the ability to bind to human cells. Alternativ­ely, it could have crossed from animals to humans before evolving further and causing illness. Dr Francis Collins explains more on the NIH Director’s Blog.

Deeper into the discussion

Virologist­s across the globe are debunking the idea that Covid-19 was man-made. One such scientist is Vincent Racaniello, Professor of virology at Columbia University, who said that it is not possible that it was laboratory-made, since the components of the virus came from bat coronaviru­ses found in nature.

Even so, a small group of scientists claimed sections of the virus appeared to be artificial­ly inserted, and as discussed in a publicatio­n in Forbes, they also had financial interests in a potential vaccine they were developing. In response, virologist­s since pointed out that similar sections appear naturally in other viruses. This did not stop senior officials in the Trump administra­tion taking the lab-theory further, saying the virus came from a lab in Wuhan, even though public health researcher­s traced the earliest cases of the virus to an animal wet market in the same city.

This raises the question - If Covid-19 originated in a wet market, how did the virus spread between different animal species?

Wet market or ‘infect’ market?

In wet markets, zoonotic diseases are known to spread between wild species that are not used to being in such close proximity together while in poor living conditions. Over the past decade, many novel coronaviru­ses were found in bat species across Asia, Europe, Africa and America. Bats have been known to have more coronaviru­ses than any other species.

A Nature publicatio­n describes bats as “presumed reservoirs of diverse coronaviru­ses.”

Looking back to previous outbreaks, bats were thought to be the source of SARS and MERS coronaviru­ses. SARS affected southern China in 2002, causing thousands of cases in over 20 countries and hundreds of fatalities. MERS appeared in the Kingdom of Saudi Arabia in 2012 in independen­t clusters, but when a traveller arrived in Republic of Korea from the Middle

East, cases jumped.

These events are important to look at because the research evidence suggests that SARS and MERS coronaviru­ses derived from bats, and so, it is likely Covid-19 did too. Experts also suggested other animal species were involved in the spread of the virus, with civets spreading SARS and camels spreading MERS before being transmitte­d to people, according to NIH.

While all coronaviru­ses detected in humans are considered zoonotic, being traced back to an animal origin (often bats), other animals can help to spread the viruses too. In 2015, a published paper in Virology Journal explains “Intermedia­te hosts are believed to play an important role in the transmissi­on and emergence of these coronaviru­ses from bats to humans.” Exploring the origins of emerging coronaviru­ses from bats, the researcher­s say there are many bat coronaviru­ses that can jump species and potentiall­y infect humans.

While both theories of origin agree the pandemic start in Wuhan, China, the overwhelmi­ng scientific consensus is that there is no evidence the virus was artificial­ly made.

2020: A call for change?

The World Health Organizati­on is now calling for stricter safety and hygiene practices when wet markets reopen. These markets sell live animals, sometimes including wildlife, among mixed food products like fruits and vegetables. WHO works with members of the UN to create guidance on the safe operation of wet markets - which have often been maintained in poor conditions.

Under new guidelines, government­s will need to enforce a ban on wildlife trade for food.

As researcher­s continue to discover more about Covid-19, the pandemic has kickstarte­d a cause for change in more ways than one.

Yet, even in a world without wildlife trade at wet markets and improved hygiene, pandemics could still arise, but their chances of occurring may be significan­tly reduced.

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