19 March 2020
The COVID-19 pandemic is caused by a new coronavirus called SARS-CoV-2. Since the emergence of the SARS-CoV-2 virus in Wuhan, China, scientists have been looking at how and where it originated.
And now, based on analysis of the virus’ genetic material, they have found that the SARS-CoV-2 virus originated through natural processes. There is no evidence that the virus was made in a laboratory or that it has been engineered by humans in any way.
Diseases that originate in animals and then ‘jump’ into humans are known as zoonoses. Understanding how and why this happens may help to prevent future zoonotic infections.
Coronaviruses are not new. This latest virus – SARS-CoV-2 – is the seventh coronavirus that we know can infect humans. Other coronaviruses cause some common colds, and the diseases SARS and MERS. The coronaviruses that cause SARS and MERS also originated in animals.
With SARS-CoV-2, by looking at its genome (the genetic material necessary to replicate the virus), the researchers have found clues to the origin of the virus and also how it has evolved.
They propose 2 scenarios that explain its origin. Where they differ, mainly, is at what point SARS-CoV-2 became capable of causing disease in humans.
- Scenario 1: The virus evolved by natural selection in a non-human host before jumping into humans. It was capable of causing disease in humans from the get-go. Various animals have been put forward as potential hosts, including bats. Given there is no recorded bat to human transmission, there may also be an intermediate host between the bats and humans.
- Scenario 2: A non-pathogenic version of the virus transferred from animals into humans, and then subsequently, during human-to-human transmission has evolved pathogenic features – meaning it has become capable of causing disease.
If scenario 1 is correct, then there is the possibility that there may be future outbreaks, as the disease-causing strain of the virus would still be circulating in the animal population and could re-infect humans.
