In December 2019, China reported the first case of Covid-19 and within a few months, it has spread to more than 207 countries, infecting around 21 million and killing 775,937 to date. The impact of this pandemic is huge, as it has brought down the whole world on its knees. There are some hopes that by the end of the year it will be mostly gone, however, by then the damage it will cause, will be unprecedented.
While scientists across the globe have focussed their attention on understanding this virus, in a bid to find the cure, there is uncertainty on several aspects of the origin of Covid-19. Several conspiracy theories on the origin of the virus are floating on the news portal and social media. One of the conspiracy theory has received support from highest level as countries like USA and India have taken an official stand that virus was originated from a virology lab in a city Wuhan, China, however many others have refuted these claims and backed the Scientific view that it is extremely unlikely that Covid-19 could be a deliberate product of genetic engineering in a laboratory.
However, are the scientific evidence to refute these conspiracies good enough? Let’s examine some of the evidence here. First most, the Covid-19 is not the first coronavirus which has infected and has caused devastation in human, historically, there are many coronaviruses which have often infected human and commonly causes respiratory diseases; the common cold virus, severe acute respiratory syndrome (SARS)-related coronaviruses which caused a pandemic in 2002-2003 and middle east respiratory.
Also, it is highly likely that Covid-19 passed to the human same way that the SARS or MERS virus spread –jumped from bats to cat-like civets/camels before infecting humans (zoonotic transfer). Although it is not confirmed yet, most likely the
intermediate animal through which Covid-19 passed to humans is the pangolin (scaly animals, looks similar to anteaters). However, the possibility of the Covid-19 virus directly evolving in humans itself before leading to human-human transfer has not been ruled out.
What causes these viruses to jump from animals to humans? Well, the ancestors of Covid-19 have lived in bats or other animals for so long that it can no longer capable to replicate in them and make them sick, and viruses which constantly keep mutating have recently mutated in such a way that it allowed to enter and infect humans.
Genetically coronavirus enters to humans via binding its spike proteins to a protein known as ACE2 (angiotensin-converting enzyme 2) present on the surface of cells in the lungs, heart, and intestine. Interestingly, the protein sequence of viral spikes protein which allows the virus to bind to human ACE2 is very similar to coronaviruses in pangolin but not with the sequence available from bats coronaviruses, suggesting pangolin as the intermediate host of transmission to human rather bats directly. This route is in line with the known mode of transmission of coronaviruses, earlier cats and camels were the intermediate host and now it could be pangolin.
In China, pangolin meat and scales are highly-priced and these illegally traded animals are frequently used in traditional Chinese medicine (TCM). Another concrete evidence that covid-19 has comes through natural selection and not through genetic manipulation in a laboratory, has come from the genetic sequence (genome) of the virus itself.
China released the first genome sequence of Covid-19 in January 2020 and since then its genome has been sequenced thousands of time and available for researchers to study the origin of coronavirus, the comparative analysis of these sequences available from various labs worldwide, can also help to track the virus route across the world. If it had been genetically engineered or manipulated, we would expect to see signs of an inserted gene sequence.
The Coronaviruses are subjected to extensively study since 2002 after the SARS pandemic and many labs across the globe are studying these viruses. To study viruses in the laboratory, the scientist needs backbones (a stretch of genomic sequence which helps researchers in infecting cells or animals with viruses. So, in a scenario, for a virus to come from a lab, backbone sequence should have been there in the Covid-19 genome sequence however all the available genome sequence data have conclusively shown that Covid-19 is not derived from any known viral backbone.
Using the available genomics and structural data scientist has also identified that Covid-19 has evolved to specifically bind to human ACE2 and its less efficient in a bind to ACE2 protein in many animals like cats, dogs, and cattle which suggest that virus was the result of natural selection. Of the known human pathogen, viruses constitute a large proportion of emergingpathogens.
Since 1980, among emerged viruses, 75 percent have been transferred
to humans through an intermediate animal host. Hence, to be prepared for any other future outbreak, animal species, specifically those who are in the direct human contacts need to be routinely screened for the viruses. At the same time scientist needs to develop cost-effective tools for better routine detection, prevention, and finding a cure for infectious diseases and associated comorbidities.
The Covid-19 has taught a big lesson to the whole world, that through science we can effectively detect and manage these disease threats, and hence there is more needs to invest in scientific research than ever before.
