Was the coronavirus created in the laboratory? The scientist replies

While the new coronavirus that causes COVID-19 is spreading worldwide, with cases that now exceed 284.000 worldwide (March 20), disinformation is spreading almost as quickly.

A persistent myth is that this virus, called SARS-CoV-2, was produced by scientists and fled a laboratory in Wuhan, China, where the outbreak began.

A new analysis of SARS-CoV-2 could finally silence this latter idea. A team of researchers has compared the genome of this new coronavirus with the other seven coronaviruses known to infect humans: SARS, MERS and SARS-CoV-2, which can cause serious diseases; along with HKU1, NL63, OC43 and 229E, which typically cause only mild symptoms, the researchers wrote on March 17 in the journal Nature Medicine.

"Our analyzes clearly show that SARS-CoV-2 is not a specially constructed laboratory construct or virus," they write in the journal article.

Kristian Andersen, associate professor of immunology and microbiology at Scripps Research, and his colleagues examined the genetic model for the proteins of the spikes protruding from the surface of the virus. The coronavirus uses these spikes to grab the outer walls of its host cells and then enter those cells. In particular, they examined the gene sequences responsible for two key characteristics of these peak proteins: the grabber, called the receptor binding domain, which engages with host cells; and the so-called cleavage site that allows the virus to open up and enter those cells.

This analysis showed that the "hooked" part of the peak had evolved to target a receptor outside human cells called ACE2, which is involved in regulating blood pressure. It is so effective in binding to human cells that the researchers claimed that the peak proteins were the result of natural selection and not genetic engineering.

Here's why: SARS-CoV-2 is closely related to the virus that causes severe acute respiratory syndrome (SARS), which suffocated around the world around 20 years ago. Scientists investigated how SARS-CoV differs from SARS-CoV-2 - with several changes to the key letters in the genetic code. Yet in computer simulations, mutations in SARS-CoV-2 don't seem to work very well to help the virus bind to human cells. If scientists had deliberately designed this virus, they would not have chosen mutations that computer models suggest would not work. But it turns out that nature is smarter than scientists and the novel coronavirus found a way to change that was better - and completely different - than anything scientists could have created, the study found.

Another nail in the theory "escaped from the evil laboratory"? The overall molecular structure of this virus is distinct from known coronaviruses and instead closely resembles the viruses found in bats and pangolins that had been poorly studied and never known to cause human harm.

"If someone was trying to design a new coronavirus as a pathogen, he would have built it from the backbone of a virus known to cause disease," according to a Scripps statement.

Where does the virus come from? The research team has come up with two possible scenarios for the origin of SARS-CoV-2 in humans. One scenario follows the origin stories of some other recent coronaviruses that have wreaked havoc on human populations. In that scenario, we contracted the virus directly from an animal - civets in the case of SARS and camels in the case of Middle East respiratory syndrome (MERS). In the case of SARS-CoV-2, the researchers suggest that the animal was a bat, which transmitted the virus to another intermediate animal (probably a pangolin, some scientists said) which carried the virus in humans.

In that possible scenario, the genetic characteristics that make the new coronavirus so effective in infecting human cells (its pathogenic powers) would have been in place before moving on to humans.

In the other scenario, these pathogenic features would only evolve after the virus had passed from the animal host to man. Some coronaviruses originating from pangolines have a "hook structure" (that receptor binding domain) similar to that of SARS-CoV-2. In this way, a pangolin has transmitted its virus directly or indirectly to a human host. So once inside a human host, the virus could have evolved to have its other invisible feature: the cleavage site that allows it to easily break into human cells. Once this ability was developed, researchers said that coronavirus would be even more capable of spreading among people.

All these technical details could help scientists predict the future of this pandemic. If the virus entered pathogenic human cells, this increases the likelihood of future outbreaks. The virus could still circulate in the animal population and could jump back to humans, ready to cause an outbreak. But the chances of such future outbreaks are less if the virus is to enter the human population first and then evolve pathogenic properties, the researchers said.