SARS-CoV-2 Cases Reported on International Arriving and Domestic Flights: United States, January 2020-December 2021

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 80715 persons meeting our inclusion criteria; 67445 persons (83.6%) had at least 1 symptom reported. Of 67445 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)

Automated summary

This study examined trends in the number of COVID-19 infectious travelers in relation to vaccination rates and overall SARS-CoV-2 cases in the United States. The majority of travelers were asymptomatic during travel, indicating unknowing transmission. During periods of high community transmission, vaccination and mask-wearing are important for reducing the risk of transmission.