Mobility and the spatially heterogeneous spread of SARS-CoV-2 in Belgium

Given that social interactions drive the spread of infectious diseases amongst humans, one anticipates that human mobility in Belgium affected the spread of COVID-19 during both 2020 "waves". Measures against this spread in turn influenced mobility patterns. In this study, we analyse and mutually compare time series of COVID-19-related data and mobility data across Belgium's 43 arrondissements (NUTS 3 level). First, we confirm that overall mobility did in fact change significantly over the consecutive stages of the pandemic. So doing, we define a quantity that represents the degree of mobility between two arrondissements: the "connectivity index". Second, we analyse spatio-temporal COVID-19-related incidence and hospitalisation data using dynamic time warping and time-lagged cross-correlation. This allows us to quantify time lag and morphological similarities between localised waves. Third, by coupling those analyses, we conclude that mobility between arrondissements is in fact indicative of the spatio-temporal spread of COVID-19 in Belgium, as was previously shown for other EU countries. This conclusion supports the need for mobility analysis and/or control during a pandemic, and by extension motivates the development of our spatially explicit Belgian metapopulation model.