Speaker
Description
By the end of 2020, a nationwide SARS-CoV-2 genomic surveillance consortium was established in Belgium. During this period, emphasis was placed on the real-time analysis of circulating variants and case studies. Moving away from real-time analyses, our focus now shifts towards exploiting the resulting comprehensive set of SARS-CoV-2 sequences to perform a retrospective analysis on the introduction and dispersal dynamics of the main variants of concern (VOC) having invaded Belgium (Alpha, Delta, Omicron BA1, BA2, and BA5). Specifically, our aims are (i) to compare the ‘ability’ of those different variants to establish sustained transmission chains and spread across the country, and (ii) to evaluate the drivers of their dispersal at national scale.
We collected >177,000 SARS-CoV-2 VOCs genomes from the last two years of genomic surveillance in Belgium (GISAID, June 2023) and retrieved location information at the zip code level. Pairwise measures of human mobility data across Belgium was obtained from the Data for Good database. We first identified different clades corresponding to distinct introduction events into the country. To minimize potential underestimation of the number of circulating clades, we explored different strategies during the discrete phylogeographic analysis, such as using background datasets of different sizes and/or different levels of administrative precision (i.e., country, provinces). With our clades
defined, we are currently performing discrete and continuous phylogeographic analyses for each variant to (i) reconstruct their spatial spread, and estimate and compare dispersal statistics (e.g., weighted diffusion coefficient), and (ii) test the impact of human connectivity and mobility on their dispersal frequency and velocity.
Through studying the ‘ability’ of a variant to penetrate and disperse within a highly connected and densely populated, yet spatially heterogeneous, country like Belgium, we hope to contribute insights for a retrospective evaluation of the pandemic, preparing for potential future public health crises.
