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Updated: Jul 26, 2025

Author Spotlight: Advancements in Multiplex Detection of Respiratory Viruses
Published on: November 10, 2023
SARS-CoV-2 Cases Reported on International Arriving and Domestic Flights: United States, January 2020-December 2021
Leigh Ellyn Preston1, Araceli Rey1, Simone Dumas1
1Leigh Ellyn Preston, Araceli Rey, Simone Dumas, Andrea Rodriguez, Alida Gertz, Kristin C. Delea, Francisco Alvarado-Ramy, Deborah L. Christensen, Clive Brown, and Tai-Ho Chen are with the CDC COVID-19 Ports of Entry Team, Atlanta, GA.
Abstract:
Objectives. To describe trends in the number of air travelers categorized as infectious with SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2; the virus that causes COVID-19) in the context of total US COVID-19 vaccinations administered, and overall case counts of SARS-CoV-2 in the United States. Methods. We searched the Quarantine Activity Reporting System (QARS) database for travelers with inbound international or domestic air travel, a positive SARS-CoV-2 lab result, and a surveillance categorization of SARS-CoV-2 infection reported during January 2020 to December 2021. Travelers were categorized as infectious during travel if they had arrival dates from 2 days before to 10 days after symptom onset or a positive viral test. Results. We identified 80 715 persons meeting our inclusion criteria; 67 445 persons (83.6%) had at least 1 symptom reported. Of 67 445 symptomatic passengers, 43 884 (65.1%) reported an initial symptom onset date after their flight arrival date. The number of infectious travelers mirrored the overall number of US SARS-CoV-2 cases. Conclusions. Most travelers in the study were asymptomatic during travel, and therefore unknowingly traveled while infectious. During periods of high community transmission, it is important for travelers to stay up to date with COVID-19 vaccinations and consider wearing a high-quality mask to decrease the risk of transmission. (Am J Public Health. 2023;113(8):904-908. https://doi.org/10.2105/AJPH.2023.307325).
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