Human mobility drives geographical diffusion of airborne infectious diseases at different scales, and the COVID-19 pandemic has made mobility data widely available thanks to technological advances. Mobility has been used to investigate COVID-19 but few studies focus on mobility itself. We used public data from February 14th 2020 to May 9th 2021 in Spain to characterize mobility patterns between the 52 provinces to build the Epidemic Diffusion Network using network science methods to study geographical diffusion phenomena.
A total of 135 (out of 2.264) connections between the 52 provinces were identified as the most relevant and a weighted, directed network was built. Madrid, Valladolid and Araba/Álaba scored the highest degree and strength. Shortest routes (most likely path between two points) were obtained between all provinces A total of 7 mobility communities were found with a network modularity of 63%. COVID-19 cumulative incidence in 14 days (CI14) reflected community structure, with provinces of the same cluster behaving more similar when compared with the outside ones. Shortest routes of diffusion between all 52 provinces were obtained.
Mobility patterns in Spain are governed by a small number of high-flow connections that remain constant in time and seem unaffected by seasonality or restrictions. Most of the travels happen within communities, that does not completely represent political borders, thus indicating the importance of coordination between administrations when addressing health emergencies. The most likely geographical spread pattern in Spain is wave-like with occasional long-distance jumps, like a small-word network. This information could be of use to enhance preparedness and response plans with interventions targeted to relevant locations before the disease spreads, and to inform better models of disease diffusion at the country level.