Outbreak dynamics of COVID-19 in Europe and the effect of travel restrictions

Abstract

For the first time in history, on March 17, 2020, the European Union closed all its external borders in an attempt to contain the spreading of the coronavirus 2019, COVID-19. Throughout two past months, governments around the world have implemented massive travel restrictions and border control to mitigate the outbreak of this global pandemic. However, the precise effects of travel restrictions on the outbreak dynamics of COVID-19 remain unknown. Here we combine a global network mobility model with a local epidemiology model to simulate and predict the outbreak dynamics and outbreak control of COVID-19 across Europe. We correlate our mobility model to passenger air travel statistics and calibrate our epidemiology model using the number of reported COVID-19 cases for each country. Our simulations show that mobility networks of air travel can predict the emerging global diffusion pattern of a pandemic at the early stages of the outbreak. Our results suggest that an unconstrained mobility would have significantly accelerated the spreading of COVID-19, especially in Central Europe, Spain, and France. Ultimately, our network epidemiology model can inform political decision making and help identify exit strategies from current travel restrictions and total lockdown.

Keywords: COVID-19; Coronavirus; SEIR model; epidemiology; outbreak control; outbreak dynamics.

Figure 1.. COVID-19 outbreak dynamics across Europe.

Mobility network of the European Union with N = 27 nodes and the 172 most traveled edges (top left); basic reproduction number R₀ = C/B (top right); initial community spread ρ = E₀/I₀ (bottom left); and affected population η = N*/N (bottom right).

Figure 2.. COVID-19 outbreak dynamics across Europe.

Reported infectious and recovered populations and simulated exposed, infectious, and recovered populations. Simulations are based on a parameter identification of the basic reproduction number R₀ = C/B, the initial community spread ρ = E₀/I₀, and the affected population η = N*/N for each country for given disease specific latent and infectious periods of A = 2.56 days and C = 17.82 days. The day d₀ indicates the beginning of the outbreak at which 0.001% of the population are infected.

Figure 3.. COVID-19 outbreak control across Europe.

Effect of travel restrictions. Constrained mobility with travel restrictions (top) vs. unconstrained mobility without travel restrictions (bottom). Simulations are based on latent, contact, and infectious periods of A = 2.56 days, B = 4.07 days, and C = 17.82 days, and mobility coefficients of ϑ = 0.00 (top) and ϑ = 0.43 (bottom).