Coronavirus may have circulated among humans for years before mutation made it lethal, says study
The novel coronavirus struck China in December 2019, but a lot about its initial whereabouts is still a mystery. Now, scientists have come up with a new theory to explain its origins.
According to the theory, the new coronavirus may have circulated undetected among humans for years before wreaking havoc. Currently, the virus has spread to 181 countries or regions, after infecting 1,202,827 people and killing 64,774 people.
Talking about the importance of figuring out its origins, they said, "Amid the global COVID-19 public-health emergency, it is reasonable to wonder why the origins of the pandemic matters. Detailed understanding of how an animal virus jumped species boundaries to infect humans so productively will help in the prevention of future events."
They believe the ancestor of the new coronavirus may have jumped into humans. At that point, the virus did not pose threats, but it moved discreetly from one to another, for years. As it spread, it may have adopted new features, helping it become dangerous and often life-threatening.
These new adaptations helped the pandemic to take off, producing a sufficiently large cluster of cases to trigger surveillance, the authors wrote in their study.
What could have happened?
The scientists explain that pangolin coronaviruses could be the ancestors of the new coronavirus. The two are linked by proteins called spikes.
Spikes are proteins that stick out on the outer surfaces of coronaviruses. This protein helps the virus attach into and infect host cells such as humans or pangolins.
Both the new coronavirus and the pangolin coronavirus have a similar spike structure. "A coronavirus from a pangolin could have been transmitted to a human, either directly or through an intermediary host such as civets or ferrets," they explained.
A pangolin either directly or indirectly passed its virus onto a human host. Then, once inside a human host, the virus may have adapted further, introducing new changes to the spike protein, helping it infect humans more efficiently. Once it developed that capacity, the researchers said, the coronavirus would have become even more capable of spreading between people.
If this theory turns out to be true, the chances of a harmless coronavirus entering the human population and then changing to become dangerous are low, they said.
Alternatively, the authors speculate another scenario could be at play here. Here, they believe the new coronavirus may have developed its capacity of hurting and spreading between humans in animals itself. This means the virus may have triggered an outbreak immediately after infecting humans.
On the other hand, the scenario points to a grim situation. It raises the probability of future outbreaks, as the illness-causing strain of the virus could still be circulating in the animal population and might once again jump into humans.
To confirm which of the theories hold weight, scientists will have to look for antibodies against the virus in human blood. These studies could also be informative, "and a few such studies have been conducted showing low-level exposures to SARS-CoV-like coronaviruses in certain areas of China," the authors explained.