FIG. 4. Travel volume and contribution of imported infections.

Travel from Spain to other European countries resumed in July (though low compared to previous years). Assuming that travel returnees are infected at the average incidence of Spanish province they visited and transmit the virus at the rate of their resident population, imports from Spain are expected to account between 2 and 12% of SARS-CoV-2 cases after the summer. Traveler incidence is calculated using case and travel data at the level of provinces. Note that this model only accounts for contribution of summer travel and that stochastic fluctuations and other variants after the summer will results in further variation in the frequency of 20E (EU1). See Methods and Fig. S8.