ArticleBMJ open2021
COVID-19 infection among international travellers: a prospective analysis.
Article in BMJ open, 2021. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 6 papers.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
6 citing papers in PubMed.
- Imported SARS-CoV-2 Infections at N'djili International Airport in Kinshasa, Democratic Republic of Congo: An Epidemiological and Genomic Analysis.Influenza and other respiratory viruses · 2026Article
- Real-time surveillance of international SARS-CoV-2 prevalence using systematic traveller arrival screening: An observational study.PLoS medicine · 2023Observational
- Lessons learned from the Alberta Border Testing Pilot Program.Frontiers in health services · 2023Article
- SARS-CoV-2 infections among asymptomatic individuals contributed to COVID-19 cases: A cross-sectional study among prospective air travelers from Ghana.Frontiers in public health · 2022Article
- Effect of Omicron on the prevalence of COVID-19 in international travelers at the Mexico city international airport. December 16th, 2021 to January 31st, 2022.Travel medicine and infectious diseaseArticle
- International air travel-related control measures to contain the Covid-19 pandemic: A companion review to a Cochrane rapid review.New microbes and new infectionsReview
Corrections and comments
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Authors and funding
14 authors.
Funding
Abstract
objectivesThis report estimates the risk of COVID-19 importation and secondary transmission associated with a modified quarantine programme in Canada. DESIGN AND
participantsProspective analysis of international asymptomatic travellers entering Alberta, Canada.
interventionsAll participants were required to receive a PCR COVID-19 test on arrival. If negative, participants could leave quarantine but were required to have a second test 6 or 7 days after arrival. If the arrival test was positive, participants were required to remain in quarantine for 14 days.
main outcome measuresProportion and rate of participants testing positive for COVID-19; number of cases of secondary transmission.
resultsThe analysis included 9535 international travellers entering Alberta by air (N=8398) or land (N=1137) that voluntarily enrolled in the Alberta Border Testing Pilot Programme (a subset of all travellers); most (83.1%) were Canadian citizens. Among the 9310 participants who received at least one test, 200 (21.5 per 1000, 95% CI 18.6 to 24.6) tested positive. Sixty-nine per cent (138/200) of positive tests were detected on arrival (14.8 per 1000 travellers, 95% CI 12.5 to 17.5). 62 cases (6.7 per 1000 travellers, 95% CI 5.1 to 8.5; 31.0% of positive cases) were identified among participants that had been released from quarantine following a negative test result on arrival. Of 192 participants who developed symptoms, 51 (26.6%) tested positive after arrival. Among participants with positive tests, four (2.0%) were hospitalised for COVID-19; none required critical care or died. Contact tracing among participants who tested positive identified 200 contacts; of 88 contacts tested, 22 were cases of secondary transmission (14 from those testing positive on arrival and 8 from those testing positive thereafter). SARS-CoV-2 B.1.1.7 lineage was not detected in any of the 200 positive cases.
conclusions21.5 per 1000 international travellers tested positive for COVID-19. Most (69%) tested positive on arrival and 31% tested positive during follow-up. These findings suggest the need for ongoing vigilance in travellers testing negative on arrival and highlight the value of follow-up testing and contact tracing to monitor and limit secondary transmission where possible.
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