Figure 3.

Change in population-level transmission of SARS-CoV-2 between origin and destination cities for airline travellers at various infection incidences by test-and-travel strategy

For each strategy, we calculated the ratio of cumulative infectious days in an origin city relative to a destination city under different assumptions of SARS-CoV-2 infection incidence for both locations. The ratio is represented by the coloured boxes, where boxes in darker reds are high ratios (corresponding to higher importation risk) and yellow is lower ratios (corresponding to lower importation risk). The white boxes represent scenarios where the ratio is less than one, meaning travellers are moving from a low to high incidence city (corresponding to minimal relative importation risk). Test-and-travel strategies had the largest effect when they reduced the ratio of cumulative infectious days compared with base case (no testing), as shown by a shift from darker colour to lighter colour for a given incidence scenario.