There is an increasing amount of evidence that the novel coronavirus, SARS-CoV-2, was present in the global population before testing could confirm cases in January 2020.

While there is no scientific consensus on the origins of the virus, researchers across the world are discovering traces of SARS-CoV-2 in wastewater dated from 2019. 

READ MORE: Sewage could be the 'canary in the coal mine' for COVID-19 second wave

In June, a study showed that 40 tested sewage samples from Milan and Turin had traces of the virus in December 2019. 

In Brazil, the Federal University of Santa Catarina tested wastewater samples from the 27 November 2019, finding the presence of SARS-CoV-2. 

Evidence suggests the coronavirus may have also been present in France last year, as a retrospective study conducted by the Albert Schweitzer hospital highlighted the similarity in chest x-rays of pneumonia patients in 2019 with COVID-19 patients in 2020. 

The clusters of the virus, pre-2020, is conducive with the beginnings of a pandemic, explains Karol Sikora, a former World Health Organization director, who spoke to CGTN Europe's Razor team. 

"The virus obviously has to arrive somewhere and then it travels. Now, the French cases, it wasn't a pandemic then, it was just a little handful. And that's how pandemics begin. Little clusters. And then it passes away. It's also how pandemics end with little clusters. And then it moves into the big time. And the airline routes ... are clearly the way it's spread," says Sikora.

Despite these studies, there is far more work yet to be done to determine the virus's origin. 

"This would suggest that the viral spread was far larger earlier than what we thought and where it originated from, how it's adapted, when it's adapted, we don't know," says Tom Jefferson, an epidemiologist at the University of Oxford. "You get that from every researcher you speak to. We need more data and more data."

"The question then becomes exactly what wakes them up and what makes them aggressive. What conditions makes them aggressive. I'm afraid I don't have an answer to that," added Jefferson. 

Ultimately, identifying how the outbreak began can both help stop future pandemics, and benefit in the ongoing fight against COVID-19. 

Check out our new six-part podcast series Notes on a Pandemic as CGTN Europe finds out how business, science and people have risen to the challenge of COVID-19. 

Video editor: Sam Cordell