Restrictions on international travel were a key intervention to slow the spread of COVID-19, study shows

Research into the transmission of COVID-19 variants to and across Canada shows that restrictions on international travel have been a key intervention to reduce or slow the spread, according to a report released today. increase. e-life.

The results suggest that a dynamic travel ban could give governments more time to prepare for new variants by reducing the number of virus imports that could cause domestic outbreaks. . contact tracing and vaccination programs.

The COVID-19 pandemic has highlighted the importance of genomic epidemiology. That is, to genetically sequence SARS-CoV-2 samples from different regions and time periods to understand the origin and movement of international viral variants, especially those of concern or interest. These methods have been widely used in the UK, US, Brazil, New Zealand and Europe, demonstrating differences in epidemic dynamics between countries that have adopted different public health approaches to contain the virus.

Large-scale SARS-CoV-2 genomic epidemiologic analyzes in Canada have so far been limited to studies of early outbreaks within Quebec. We wanted to elaborate on this study using a nationwide analysis of COVID-19 first and second waves. He also wanted to assess the impact of the March 2020 international travel restrictions on international imports of the virus and understand why the virus persisted into his 2021. “

Angela McLaughlin, Lead Author, British Columbia Center for Excellence HIV/AIDS, Research Assistant, University of British Columbia, Canada, PhD Candidate in Bioinformatics

The team used available sequence data from Canadian COVID-19 cases and data on the prevalence of variants circulating in other countries to deduce the geographic origin of the virus. From this, they identified the introduction of over 2,260 new subspecies of him to Canada. It contains 680 substrains. This is a virus that was introduced from another country and has become circulating within the Canadian population. They also identified 1,582 singletons. This was an introduced virus that did not appear to be circulating within the Canadian population.

Import rates hit the highest (58.5 substrains per week) just as travel restrictions were introduced in April 2020, including 31.8 from the US and 31.2 introduced only in Quebec . Two weeks after the travel restrictions took effect, the overall substrain import rate dropped 3.4-fold, and within 4 weeks it fell 10.3-fold.

However, despite these declines, new virus variants continued to be introduced at low levels until August 2020, when a small spike led to a second wave. This suggests that the wild-type substrain introduced in the summer, when prevalence and immunity were low, had the highest proportion of his COVID-19 cases in the second wave. Equivalently, this means that even low levels of ongoing virus imports of similarly contagious variants may contribute to virus persistence. Further easing of restrictions and a rapid recovery in import rates contributed to the second wave.

By classifying sources among state, state, US, and other international sources, the team was able to ascertain where the new virus was imported from. They found that most first-wave virus introductions (January to July 2020) originated from the United States, followed by Russia, Italy, India, Spain, and the United Kingdom, and were imported primarily to Quebec and Ontario. I found In the second wave (August 2020 to end-February 2021), the origin of the new substrain is still dominated by the United States, with increasing relative contributions from India, the United Kingdom, Asia, Europe and Africa. did.

That the United States was a large contributor of COVID-19 cases in 2020 was unexpected by the authors given the high prevalence of COVID-19 throughout 2020 and the long land borders shared between the two countries. It wasn’t. Even if the number of international arrivals to Canada fell by 77.8% from 2019 to 2020, the number of truck drivers and crew (airplanes, ships, trains) fell only 24.8%, compared with April 2020. It accounts for almost half of all international arrivals. The arrival of essential key workers supporting his supply chain may have inadvertently facilitated additional imports from the United States. This suggests that better public health measures, such as contact tracing and rapid testing, are one area where they may have helped prevent the movement of the new variant.

“These analyzes shed light on the natural epidemiological history of SARS-CoV-2 in the context of public health interventions and use substrain-based genomic surveillance to identify gaps in national epidemic responses. shows how,” concludes senior author Jeffrey Joy. HIV/AIDS Research Fellow, British Columbia Center for Excellence; Assistant Professor, University of British Columbia School of Medicine. “Broad and prolonged restrictions on non-essential international travel are not necessarily desirable policies given their economic impact. Suggests a swift and strict travel ban to the region, seriously considering the transmission of an entirely new virus that has yet to be identified in the country, potentially sowing the seeds of multiple simultaneous outbreaks and an overwhelmed health care system. should be reduced.”