University genome study finds Quebec COVID-19 strain originated in Europe and the Americas, not Asia

Representation of national and international transmissions of SARS-CoV-2 variants during the months of February and March 2020. The color represents the geographic origin of the cases. At least 247 acquisitions led to the emergence of the epidemic in Quebec. Source: INSPQ

A COVID-19 genetic sequencing study out of McGill University shows that around 250 infections during spring break led to 60,000 positive cases, almost all of them from Europe or the Americas.

The McGill Genome Centre and INSPQ (Institut national de santé publique du Québec) study into the SARS-CoV-2 genome (the virus responsible for the COVID-19 outbreak) found it could have been carried by as few as 247 people.

"Our research indicates that origin of the outbreak in Quebec was mostly via Europe and the Americas, and not from Asia," said Dr. Jesse Shapiro, Associate Professor, Department of Microbiology and Immunology in a release. "Most of the early introductions of the virus into Quebec did not give rise to sustained transmission, but a barrage of introductions just after spring break eventually gave rise to the tens of thousands of cases we have seen since."

Peer review of this preliminary study is pending.

The 734 genome sequences studied were obtained btween mid-February and April 1 and contextualized within the 21,935 sequences from elsewhere in Canada and internationally.

The team was trying to ascertain where the viruses came from originally.

They found, almost one-third came from Europe (32.7 per cent) and the Carribean/Latin America (31 per cent), and almost a quarter from the US (23.9 per cent).

The data showed France, at 12.1 per cent, had the highest origin in Europe.

Just 1.2 per cent of Quebec's cases came from Asia and none were from China.

"Although our findings are preliminary, thanks to these techniques we have high confidence in the data," said Dr. Ioannis Ragoussis, Professor, Department for Human Genetics and Head of Genome Sciences at McGill University.

According to the study, COVID-19 spread much more widely by the spring than earlier believed, and it is possible the first case reached Quebec City via the UK as early as Jan. 30, 2019.

"This is the first of many analyses that will look not only at how the virus was first introduced into the province but also at how it has been spreading," said Dr. Guillaume Bourque, Professor, Department for Human Genetics and Head of the Canadian Center for Computational Genomics. "Indeed, it is surprising to see how widely the virus had been dispersed at such an early stage."

The data also shows a high concentration in the Monteregie region in the early stages of the pandemic. 

The study is available online.