For months, Quebecers have wondered why their province has been the one hardest hit by COVID-19.
One popular theory blames people returning from spring break vacations abroad right before everything was locked down, and a new study using genetic sequencing seems to confirm that hypothesis.
“It was really the barrage of spring break, where you do have in a short period of time, really, lots of people,” explained Dr. Jesse Shapiro, a McGill microbiology professor and one of the study’s authors.
Shapiro and his co-authors sought to track the early spread of the virus using genetic sequencing. The team read the genetic code of the virus in 734 early Quebec COVID cases, then compared it to similar data from other countries.
“This is what we’re doing to compare these sequences and construct what we call a phylogenetic tree, so like a family tree of the viruses, that dates them back in time,” Shapiro said.
The researchers found that as few as 247 spring break travellers were at the root of Quebec’s nearly 70,000 cases. The week off ended March 9th, and those who came back from abroad circulated freely in the community for days.
Schools closed the 13th of March, the border only shut down March 18th, and non-essential businesses closed on the 23rd.
On March 16th, when Quebec counted just 50 confirmed cases of COVID-19, Montreal Public Health sent agents to Trudeau International Airport to advise returning travellers they all needed to self-isolate for 14 days, because the federal government had not yet stepped in to do so.
According to the new research, it was already too late.
“The hypothesis we had before our analysis was that the spring break had huge importance in the spread of the virus and it’s indeed the case,” said Dr. Sandrine Moreira, head of genomics and bioinformatics at Quebec’s Public Health Research Institute and another author of the study.
“When you traveled to South America and Cuba and whatever, what you bring back is sometimes isolates from viruses from Italy or Netherlands or Germany,” explained Moreira.
Shapiro believes the spread of the virus in Quebec would not have been as wide if the government had taken measures at the border earlier.
“Since the beginning of the pandemic, we have followed the advice of public health officials based on the best available evidence and science,” said Cole Davidson, a spokesperson for federal Health Minister Patty Hajdu.
He said as the science around COVID-19 has evolved, so too has the government’s response.
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