International travel during the COVID-19 pandemic: implications and risks associated with ‘travel bubbles’

Air travel is considered as the major route that facilitated the distribution of COVID-19 across international borders. Passengers with asymptomatic and pre-symptomatic SARS-CoV-2 infection can bypass the symptom-based surveillance systems established in the airports. Travel bubbles should be considered as an effective compromise in preventive strategies. Therefore, strict preventive measures have to be implemented at the entry and exit points in addition to the measures taken for preventing on-board transmission SARS-CoV-2.