How do we know where viruses come from? Experts share how they solve the mystery

It’s been about four months since the new coronavirus released its wrath on the world — killing thousands and infecting millions — but information on its origin remains unclear, scientists say.

One thing is certain, however: SARS-CoV-2, the virus driving the pandemic, was not made in a lab.

“That’s just in the comic books and movies,” Robert Garry, a professor in the Department of Microbiology and Immunology at the Tulane University School of Medicine in New Orleans, told McClatchy News.

Dr. Garry contributed to a Nature study that discusses possible origin stories for the new coronavirus and debunks the lab conspiracy theory.

For any virus that emerges in the human population, scientists follow similar steps to determine its origin so they can understand how much the pathogen changes as it hops from one person to the next, experts say.

Understanding these characteristics aid in the development of countermeasures such as diagnostic tests, drugs and eventually vaccines.

Here’s how they do it.

Sequence the genetic material of the virus

Quickly after there were reports of a viral pneumonia spreading in Wuhan, Hubei Province, researchers in China analyzed samples taken from infected patients and obtained full sequences of their genome, or genetic material.

To do this, scientists use technology that figures out the order of the nucleotides — the building blocks of genetic material — of its genome, which can be made of DNA or RNA.

The family of coronaviruses are made up of RNA, short for ribonucleic acid, which plays a role in the production of the body’s proteins.

Sequences are then usually shared with other scientists, as the Chinese researchers did with the new coronavirus, so experts around the world can assist in the next step: comparison.

Compare it to other known viruses

Hundreds of different viruses exist, but SARS-CoV-2 is the seventh pathogen that belongs to the family of coronaviruses known to infect humans, according to the Nature study.

Other coronaviruses include the SARS virus, which moved from bats to a mammal called a civet and then to humans beginning in 2002, and the Middle East respiratory syndrome, or MERS, which was transmitted from camels in 2012.

To better understand where a virus came from and how it has changed over time, scientists must compare them to existing pathogens.

In the case of COVID-19 — the disease SARS-CoV-2 causes — researchers found that its genome was 96% identical to that of an existing bat coronavirus, according to a study published in February in Nature from the Wuhan Institute of Virology.

“Ninety-six percent sounds very similar except that a four percent difference is quite a bit in evolutionary terms, probably decades,” Dr. Garry said.

But sometimes there are gaps in these pieces of information, he added, meaning more comparisons and research into the origins of past viruses must be done before taking a deeper dive into what gives viruses their power to infect humans.

Study the structure and components of the virus

Comparing the entire sequence of a virus’s genome also lends itself to the comparison of the proteins they’re made of, Dr. Garry said. These proteins are what allow the pathogen to infect humans.

Knowing this can reveal how similar, or not, some viruses are compared to others in the hopes of determining a pathogen’s origin.

SARS-CoV-2 has a spiky protein that is effective at attaching to proteins hanging outside of human cells, thus allowing the virus to enter the cells and spread in the body, Dr. Garry said.

Learning about the structure and behaviors of this spiky protein led researchers to believe the new coronavirus is a product of natural selection, and not genetic engineering in a lab, according to the Nature study.

Just when and where the virus mutated into version it is now is still unknown, Dr. Garry said.

Modeling

Scientists also use models to either confirm or deny their hypothesis on virus origins.

Computer simulations showed that mutations currently found in SARS-CoV-2 fail to successfully and effectively bind to human cells, the study said.

“It turns out, nature is smarter than scientists, and the novel coronavirus found a way to mutate that was better —and completely different — from anything scientists could have created,” LiveScience reported about the study.