Many researchers are racing to develop a vaccine to curb the spread of the novel coronavirus. But others are looking to other viruses for a solution to the pandemic. In this coronavirus news update: COVID-19 Origin, we look at the possible source of the virus.
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Coronavirus News Update: COVID-19 Origin Still A Mystery
Lab Freezers Yield Surprising Discoveries
As the pandemic intensifies, more scientists are looking at old samples for possible answers.
In Cambodia, researchers may have uncovered a close relative of the novel coronavirus, SARS-CoV-2, in frozen bat samples. In 2010, researchers captured two Shamel’s horseshoe bats (Rhinolophus shameli) in the country’s north as part of the PREDICT project.
The US-government-funded project, which ended this year, mostly surveyed bats, as well as pangolins and other animals for viruses with pandemic potential. Labs kept samples in freezers across Asia. More specifically, Malaysia, Cambodia, Laos, Nepal, Thailand, and Vietnam. We can expect a full report on these investigations soon.
However, researchers have not yet fully sequenced the new virus’s genome or published any findings. So, the full impact of the discovery is still unknown.
Preliminary virus genome sequencing, 324 base pairs long, shows similarities to SARS-CoV-2 and its closest known relative, RaTG-13, discovered in 2013 in horseshoe bats (Rhinolophus affinis) in the Chinese province of Yunnan. But it’s only a short fragment as most known coronaviruses contain roughly 30 000 base pairs.
The initial sequence is missing the instructions for crucial parts of the virus. For example, the genes that encode the spike protein that coronaviruses often rely on to enter cells. We will only know whether this virus can enter human cells once that section is sequenced.
A closely related virus or a predecessor of SARS-CoV-2 could provide insight into how the virus spread from animals to humans. But it has to share 99% of its genome with the novel coronavirus to be deemed a close relative, which is more than any known virus.
There’s only a 4% difference between RaTG13 and SARS-CoV-2 genomes. Yet, that deviation represents 40 to 70 years of evolution since they shared a mutual ancestor.
A more distantly related virus, such as a virus called Rc-o319 found in a frozen bat in Japan, may help scientists study coronaviruses’ diversity.
Scientists found the virus in a little Japanese horseshoe bat (Rhinolophus cornutus) captured in 2013. According to a paper published in early November, 81% of its genome is similar to SARS-CoV-2. While it’s too different to explain the current pandemic’s source, it may aid future viral studies.
A team of virologists at the University of Tokyo didn’t expect to find a virus so closely related to SARS-CoV-2 when they decided to retest frozen mammal samples for viruses.
Regardless, both findings are exciting and valuable because they prove that viruses closely related to the novel coronavirus are relatively common in bat species found outside China. According to Veasna Duong, a virologist at the Pasteur Institute in Phnom Penh, this was what they were hoping to find.
Thanks to the findings, researchers believe there are other as-yet-undiscovered SARS-CoV-2 relatives stored in lad freezers. More scientists across Asia are now planning to test frozen samples of bats and other mammals for antibodies.
The findings also verify that Rhinolophus bats are typical reservoirs of these viruses.
Between 2015 and 2019, scientists found several other coronaviruses in Rhinolophus bats and pangolins. So far, there is only a handful of known coronaviruses closely related to SARS-CoV-2.
Untangling the Mystery
According to the WHO, “The introduction of a new virus to the human population is one of the greatest mysteries an epidemiologist can hope to unravel.” And while it’s vital to understand how the epidemic began to prevent further introductions to the human population, unraveling the mystery may take years.
Scientists agree that the disease has an animal origin, but the big question remains: What caused it to infect humans? We know bats are reservoirs for the virus. But there’s most likely an intermediary animal that shepherded the virus to humans.
Experts will have to retrace the chain of transmission almost a year after the first case. Besides, various researchers suggest cases may have gone unnoticed long before December 2019. So, the trail may have gone cold.
In short, the obstacles are formidable, but hopefully, the latest finding put us closer to finding the source of the virus. Lastly, more SARS-CoV-2-related coronaviruses probably exist in bat populations, and it’s only a matter of time until researchers can pinpoint where the virus comes from and how it spread to humans.
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