According to one of the conspiracy theories spread during the pandemic, a new coronavirus was created in the laboratory. However, the vast majority of scientists who have studied this virus agree that it originated naturally and jumped from animals to humans, most likely from bats.
I wonder how we know that COVID-19-causing coronavirus SARS-CoV-2 is zoonotic, ie of animal origin and not artificial? The answer lies in the genetic material and evolutionary history of the virus, as well as in knowledge of bat ecology.
Sixty percent of the infectious diseases known to us humans and 75 percent of the newly emerging infectious diseases are of animal origin. SARS-CoV-2 is the newest of the seven coronaviruses found in humans; All seven of them come from animals, bats, mice or pets.
Bats are a source of viruses that cause viral infections of Ebola, rabies, nipah and hendra, Marburg viral disease; They also include strains of the influenza A virus.
Thousands of scientists from all over the world have been able to sequence the genetic makeup of the SARS-CoV-2, or “genome”, and have made the results public. If the virus was extracted in the laboratory through genetic engineering, there would inevitably be signs of manipulation in the genomic data.
These should include existing viral sequences as the backbone of a new virus and the apparent, intentional inclusion or deletion of genetic elements.
However, there is no such evidence. It is very unlikely that any of the methods used for the genetic engineering of the virus would leave a genetic signature, such as any identifiable parts of the DNA code.
The genome of SARS-CoV-2 is similar to that of bats or other coronaviruses of pangolins; All of them have a similar general genomic architecture. The differences between the genomes of these coronaviruses show the typical natural characteristics of coronaviruses. This indicates that SARS-CoV-2 evolved from a previous, wild-type coronavirus.
One of the key features that sets SARS-CoV-2 apart from other coronaviruses is a specific “drop” protein that binds well to a protein on the surface of a human cell called ACE2. As a result, this virus enters and infects various types of human cells.
Other related coronaviruses have similar characteristics, which is further evidence that these droplets are naturally occurring and not artificially added in the laboratory.
Coronaviruses and bats are involved in a long evolutionary race in which viruses are constantly evolving and invading the bat’s immune system; Bats develop to be resistant to coronavirus infections. The virus develops in many variants, most of which are destroyed by the bat’s immune system, but some of them survive and move on to other bats.
According to some scientists, SARS-CoV-2 may come from another known bat virus (RaTG13) discovered by researchers at the Ukhan Institute of Virology. The genomes of these viruses are 96 percent identical.
This figure may seem very close to you, but from an evolutionary point of view, such a difference is significant, and as these two viruses show, they must have a common ancestor. This indicates that RaTG13 is not the ancestor of SARS-CoV-2.
In fact, SARS-CoV-2 may have evolved from a viral variant that could not survive long or arose from a variant that could not survive long in bats.
At the same time, he developed the ability to penetrate the human cell and accidentally found his way to us, presumably through an intermediary animal. It is also possible that the original, safe form of the virus jumped directly into us and then became dangerous as it passed from person to person.
Mixing or “recombining” different genomes of coronaviruses in nature is one of the mechanisms by which new coronaviruses are formed. There is also additional evidence that this process must have occurred during the generation of SARS-CoV-2.
After the onset of the pandemic, it was discovered that the virus SARS-CoV-2 had begun to develop into two different strains, resulting in adaptations needed for more effective invasion into the human cell. This was to be done by a mechanism called selective clearance, which, through beneficial mutations, helps the virus to infect more of the host; Consequently, it is becoming more common in the viral population.
This is a natural process that can eventually reduce the genetic diversity between individual viral genomes.
The merit of this mechanism should be the lack of diversity in the many genomes of SARs-CoV-2 that have already been sequenced. This indicates that the ancestor of SARs-CoV-2 has been circulating in the bat population for quite some time. He then had to get mutations that allowed him to jump from bats to other species, including humans.
It is also important to remember that about one in every five mammal species on Earth is a bat; Some of them are found only in certain places, while some travel over long distances. Due to such diversity and geographical distribution, it is quite difficult to determine which group of bats SARs-CoV-2 originated from for the first time.
There is also evidence that early cases of COVID-19 occurred long ago and there is no clear link to the city animal market, which is considered to be the starting point for the pandemic. At the same time, conspiracy theories have no evidence.
It is possible that infected people accidentally brought the virus to Ukhan, particularly at its market, where a closed, crowded environment increased the chances of the disease spreading rapidly.
Among them, it is possible that one of the scientists in the coronavirus research program in Ukhan was inadvertently infected while working in the field with bats, and then the virus spread from him. In this case, the virus is still considered natural and not leaked from the lab.
Only strong science and natural environment research can understand the history and origins of COVID-19 and similar zoonotic diseases. Our ever-changing relationship with wildlife and increased contact increases the risk of new zoonotic diseases in humans.
SARS-CoV-2 is definitely not the first virus we get from animals and it will no doubt not be the last.