Pathways of spread of COVID-19 in Québec from 2020 to 2022.

Spatial and sociodemographic disparities in COVID-19 cases have been well documented in the literature although the specific pathways through which the virus spread across territories have received comparatively less attention. Yet, understanding these pathways can offer valuable insights into the progression of the pandemic and the spatial dynamics shaping COVID-19 transmission. In this study, we used a trend-surface analysis to retrospectively examine how COVID-19 diffused across Québec, Canada, drawing on provincial-wide surveillance data from 2020 to 2022. Our work shows how COVID-19 tended to spread outwards from urban centers and that its speed of spread increased substantially over time, from 6.1 km per day during Wave 1 to 24.7 km per day by Wave 7. By characterizing the spatial pathways and velocity of spread of COVID-19 in Québec, this work provides information that could support public health authorities in preparing for future pandemics and strengthening geographically informed surveillance systems.