A new study looking back at the first and second waves of the pandemic in 2020 and 2021 says that travel restrictions banning entry to Canada have significantly reduced the number of COVID-19 cases entering the country. .
Still, the researchers say, it’s still not enough to prevent new outbreaks.
In the study published in the journal eLife on Tuesday, University of British Columbia researchers looked at publicly available data on viral genome sequences collected in 2020 and early 2021 for local sources. management of specific COVID-19 transmission chains.
They found that four weeks after Canada restricted entry to most foreign nationals in March 2020, the number of COVID-19 cases crossing the border into the country dropped tenfold.
“COVID-19 imports accelerated to the top as of March 2020 but declined sharply and sharply after the travel restrictions were introduced,” said Angela McLaughlin, a doctoral candidate in bioinformatics at UBC and lead author of the study, said in the press release. release.
“The data suggests that federal travel restrictions can be effective in reducing virus imports when implemented quickly.”
But COVID-19 is here, and travel restrictions can’t stop that.
Spring and summer 2020, daily case levels were among the lowest in the nation, but circulation still occurred within the country, the study found, with chains of transmission, the study found. Specifically, it will continue until the fall of 2020.
As travel restrictions were eased in November 2020, allowing more entry into the country as well as shortened quarantine requirements, international imports of COVID-19 cases rose again. .
Variants of interest, starting with the Alpha variant, started making their way into Canada. The researchers estimate that 30 unique genetic sublines of the Alpha variant, also known as B.1.1.7, had been introduced into the country by the end of February 2021.
Many factors, such as the state of the global fight against COVID-19, including the emergence of these variants in other parts of the world, make it difficult for restrictions to travel, the researchers say. less likely to have an impact on the pandemic, the researchers said.
“Travel restrictions will gradually decrease if domestic transmission is high, if highly transmissible variants become prevalent globally, or if many individuals are exempt from restrictions,” McLaughlin said. travel and quarantine without access to rapid testing,” McLaughlin said.
On March 21, 2020, in response to the pandemic, the United States and Canada jointly closed the border to leisure travel after closing the border to most non-citizens wishing to enter. entry into this country.
Within a month of these restrictions, the researchers found that COVID-19 imports dropped from an average of 58.5 virus subtypes per week to just 10.3 within four weeks.
There are still “newly seeded substreams” in the summer of 2020 as domestic transmissions continue. Travel restrictions were eased slightly in the fall, although the US land border did not reopen to non-essential travel until August 2021.
During the first wave of the pandemic in early 2020, 49 percent of the COVID-19 virus imported into Canada likely came from the United States, the study found, mainly through Quebec and Ontario.
According to the data, the US remained the largest source of international COVID-19 to Canada for the second tranche, at 43%. Cases coming from India accounted for 16% of cases coming from outside the country in the second wave, while cases from the UK accounted for 7%.
The researchers suggest that if restrictions were kept at maximum for longer, they could prevent more transmission, but this would have consequences in other areas.
“The economic and social consequences of travel restrictions must be weighed against the risk of a bad virus entry, potentially overloading the health care system,” Mclaughlin said.
“We are in the era of infectious disease,” said Dr. Jeffrey B. Joy, associate professor in the UBC faculty of medicine and senior author of the study. “This study highlights the growing importance of genomic epidemiology, supported by the sharing of genomic sequence data, in informing and evaluating public health policy to combat current and future viral outbreaks that threaten society.”
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