A methodology for estimating SARS-CoV-2 importation risk by air travel into Canada between July and November 2021
Abstract Background Estimating rates of disease importation by travellers is a key activity to assess both the risk to a country from an infectious disease emerging elsewhere in the world and the effectiveness of border measures. We describe a model used to estimate the number of travellers infected...
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| Format: | Article |
| Language: | English |
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BMC
2024-04-01
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| Series: | BMC Public Health |
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| Online Access: | https://doi.org/10.1186/s12889-024-18563-1 |
| _version_ | 1797199124468072448 |
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| author | Rachael M. Milwid Vanessa Gabriele-Rivet Nicholas H. Ogden Patricia Turgeon Aamir Fazil David London Simon de Montigny Erin E. Rees |
| author_facet | Rachael M. Milwid Vanessa Gabriele-Rivet Nicholas H. Ogden Patricia Turgeon Aamir Fazil David London Simon de Montigny Erin E. Rees |
| author_sort | Rachael M. Milwid |
| collection | DOAJ |
| description | Abstract Background Estimating rates of disease importation by travellers is a key activity to assess both the risk to a country from an infectious disease emerging elsewhere in the world and the effectiveness of border measures. We describe a model used to estimate the number of travellers infected with SARS-CoV-2 into Canadian airports in 2021, and assess the impact of pre-departure testing requirements on importation risk. Methods A mathematical model estimated the number of essential and non-essential air travellers infected with SARS-CoV-2, with the latter requiring a negative pre-departure test result. The number of travellers arriving infected (i.e. imported cases) depended on air travel volumes, SARS-CoV-2 exposure risk in the departure country, prior infection or vaccine acquired immunity, and, for non-essential travellers, screening from pre-departure molecular testing. Importation risk was estimated weekly from July to November 2021 as the number of imported cases and percent positivity (PP; i.e. imported cases normalised by travel volume). The impact of pre-departure testing was assessed by comparing three scenarios: baseline (pre-departure testing of all non-essential travellers; most probable importation risk given the pre-departure testing requirements), counterfactual scenario 1 (no pre-departure testing of fully vaccinated non-essential travellers), and counterfactual scenario 2 (no pre-departure testing of non-essential travellers). Results In the baseline scenario, weekly imported cases and PP varied over time, ranging from 145 to 539 cases and 0.15 to 0.28%, respectively. Most cases arrived from the USA, Mexico, the United Kingdom, and France. While modelling suggested that essential travellers had a higher weekly PP (0.37 – 0.65%) than non-essential travellers (0.12 – 0.24%), they contributed fewer weekly cases (62 – 154) than non-essential travellers (84 – 398 per week) given their lower travel volume. Pre-departure testing was estimated to reduce imported cases by one third (counterfactual scenario 1) to one half (counterfactual scenario 2). Conclusions The model results highlighted the weekly variation in importation by traveller group (e.g., reason for travel and country of departure) and enabled a framework for measuring the impact of pre-departure testing requirements. Quantifying the contributors of importation risk through mathematical simulation can support the design of appropriate public health policy on border measures. |
| first_indexed | 2024-04-24T07:10:46Z |
| format | Article |
| id | doaj.art-67b54a8d18dc4bac91fc2c4f7b45b9ce |
| institution | Directory Open Access Journal |
| issn | 1471-2458 |
| language | English |
| last_indexed | 2024-04-24T07:10:46Z |
| publishDate | 2024-04-01 |
| publisher | BMC |
| record_format | Article |
| series | BMC Public Health |
| spelling | doaj.art-67b54a8d18dc4bac91fc2c4f7b45b9ce2024-04-21T11:32:45ZengBMCBMC Public Health1471-24582024-04-0124111310.1186/s12889-024-18563-1A methodology for estimating SARS-CoV-2 importation risk by air travel into Canada between July and November 2021Rachael M. Milwid0Vanessa Gabriele-Rivet1Nicholas H. Ogden2Patricia Turgeon3Aamir Fazil4David London5Simon de Montigny6Erin E. Rees7Public Health Risk Sciences Division, National Microbiology Laboratory, Public Health Agency of CanadaPublic Health Risk Sciences Division, National Microbiology Laboratory, Public Health Agency of CanadaPublic Health Risk Sciences Division, National Microbiology Laboratory, Public Health Agency of CanadaPublic Health Risk Sciences Division, National Microbiology Laboratory, Public Health Agency of CanadaPublic Health Risk Sciences Division, National Microbiology Laboratory, Public Health Agency of Canada, GuelphPhysique Des Particules, Université de MontréalEmergency Management Branch, Global Public Health Intelligence Network Tiger Team, Public Health Agency of CanadaPublic Health Risk Sciences Division, National Microbiology Laboratory, Public Health Agency of CanadaAbstract Background Estimating rates of disease importation by travellers is a key activity to assess both the risk to a country from an infectious disease emerging elsewhere in the world and the effectiveness of border measures. We describe a model used to estimate the number of travellers infected with SARS-CoV-2 into Canadian airports in 2021, and assess the impact of pre-departure testing requirements on importation risk. Methods A mathematical model estimated the number of essential and non-essential air travellers infected with SARS-CoV-2, with the latter requiring a negative pre-departure test result. The number of travellers arriving infected (i.e. imported cases) depended on air travel volumes, SARS-CoV-2 exposure risk in the departure country, prior infection or vaccine acquired immunity, and, for non-essential travellers, screening from pre-departure molecular testing. Importation risk was estimated weekly from July to November 2021 as the number of imported cases and percent positivity (PP; i.e. imported cases normalised by travel volume). The impact of pre-departure testing was assessed by comparing three scenarios: baseline (pre-departure testing of all non-essential travellers; most probable importation risk given the pre-departure testing requirements), counterfactual scenario 1 (no pre-departure testing of fully vaccinated non-essential travellers), and counterfactual scenario 2 (no pre-departure testing of non-essential travellers). Results In the baseline scenario, weekly imported cases and PP varied over time, ranging from 145 to 539 cases and 0.15 to 0.28%, respectively. Most cases arrived from the USA, Mexico, the United Kingdom, and France. While modelling suggested that essential travellers had a higher weekly PP (0.37 – 0.65%) than non-essential travellers (0.12 – 0.24%), they contributed fewer weekly cases (62 – 154) than non-essential travellers (84 – 398 per week) given their lower travel volume. Pre-departure testing was estimated to reduce imported cases by one third (counterfactual scenario 1) to one half (counterfactual scenario 2). Conclusions The model results highlighted the weekly variation in importation by traveller group (e.g., reason for travel and country of departure) and enabled a framework for measuring the impact of pre-departure testing requirements. Quantifying the contributors of importation risk through mathematical simulation can support the design of appropriate public health policy on border measures.https://doi.org/10.1186/s12889-024-18563-1COVID-19Importation riskAir travelMathematical modelPre-departure molecular testingCanada |
| spellingShingle | Rachael M. Milwid Vanessa Gabriele-Rivet Nicholas H. Ogden Patricia Turgeon Aamir Fazil David London Simon de Montigny Erin E. Rees A methodology for estimating SARS-CoV-2 importation risk by air travel into Canada between July and November 2021 BMC Public Health COVID-19 Importation risk Air travel Mathematical model Pre-departure molecular testing Canada |
| title | A methodology for estimating SARS-CoV-2 importation risk by air travel into Canada between July and November 2021 |
| title_full | A methodology for estimating SARS-CoV-2 importation risk by air travel into Canada between July and November 2021 |
| title_fullStr | A methodology for estimating SARS-CoV-2 importation risk by air travel into Canada between July and November 2021 |
| title_full_unstemmed | A methodology for estimating SARS-CoV-2 importation risk by air travel into Canada between July and November 2021 |
| title_short | A methodology for estimating SARS-CoV-2 importation risk by air travel into Canada between July and November 2021 |
| title_sort | methodology for estimating sars cov 2 importation risk by air travel into canada between july and november 2021 |
| topic | COVID-19 Importation risk Air travel Mathematical model Pre-departure molecular testing Canada |
| url | https://doi.org/10.1186/s12889-024-18563-1 |
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