A new Canadian study shows that more than half of the imported variants of the CDC virus causing the outbreak in Canada may have come from the United States.
Scholars from British Columbia, Ontario and Arizona concluded that more than half of the imported pathogen variants that caused the outbreak in Canada may have come from the United States, Russia, India, Italy and the United Kingdom, the Vancouver Sun reported.
The newly released study is based on an international database of SARS-CoV-2 gene sequences, which allows scientists to track how and where a pandemic spreads at the genetic level.
Canadian researchers say the importation of the virus slowed after international travel restrictions were implemented in March 2020, but the imported virus continued and caused outbreaks throughout the year.
Angela McLaughlin, a doctoral student at the University of British Columbia, co-authored the paper with mentor Dr. Jeff Joy and others. “We are so connected to other countries and provinces,” she said.
“People need to visit their families, and there are other reasons to travel, and each of these actions is a probable event that the virus could spread.”
She and her colleagues advocate for tougher measures to quarantine pathogens outside the country, such as the 14-day quarantine in hotels imposed on international travelers in Australia and New Zealand.
What should be done, she said, “is early and rigorous intervention, and if rigorous measures are taken early, there is no need to allow a low-level embargo to last so long, now that the public has expressed indifference to it.”
402 branches of imported virus
The study, posted on a preprinted version of the website, has not yet been published in a peer-reviewed journal.
For the study, scholars from UBC, Western University and the University of Arizona drew on an unprecedented international public library of virus sequences.
This vast database contains sequences submitted by laboratories in Canada and around the world. They used differences between genetic blueprints to build a “family tree” of SARS-CoV-2 mutations, which helped the team identify viruses imported into Canada.
They traced the origin of 402 branches of the virus that caused the outbreak to the country of origin.
This number is undoubtedly an underestimate, the paper says, because only about 1 percent of positive tests in Canada are genetically sequenced, and many infections are asymptomatic and never even diagnosed.
The researchers also found 1,380 “single viruses” that did not cause more cases once they entered Canada.
The study concluded that of the 402 branches of the virus that caused the outbreak, 218 likely came from the United States, accounting for about 54 percent of the total.
Another 29 imported variants came from Russia, 25 from Italy, 25 from India, 22 from the United Kingdom, 15 from Spain and 15 from France. 2 came from China.
The issue of the United States becoming a major source of imported viruses raises the difficult question of how to make the world’s longest defenseless border more closely guarded against viruses, the report noted.
McLaughlin said that if the data show that truck drivers are a significant source of virus importation, then goods could be handed over at the border and drivers would not cross.
Scientists have already found that Quebec and Ontario are destinations for about 80 per cent of imported viruses. At the same time, transmission between provinces is key to the current outbreak. Researchers note that measures to limit travel between provinces, similar to those in the Atlantic provinces, would go a long way.
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