The Omicron Wave in Tunisia: Dynamic, Diversity, and Phylogenetic Analyses.

The SARS-CoV-2 Omicron variant has exhibited a rapid progression around the world, but its molecular insights in North Africa remain understudied. This study characterizes the genetic diversity, dynamics, and evolutionary trends of the Omicron variant in Tunisia over a 33-month period (December 2021-August 2024). In total, 928 high-quality whole-genome sequences were considered in this study, of which 559 were retrieved from the GISAID database and 369 were generated in our laboratory. Phylogenetic analysis of the dominant subvariants (BA.1, BA.2, and BA.5) was performed using IQ-TREE. BA.2 was the predominant subvariant (38%), followed by BA.1 (24.0%), Omicron recombinants (19%), and BA.5 (18%). BA.2 diversified into JN, KP, and BN sub-lineages. Recombinants were dominated by XBB (98.8%), primarily including EG.4, XBB.1.5, and XBB.2.3.11, with rare detection of XDK and XDQ. Phylogenetic analysis revealed local clusters in BA.1, BA.2, and BA.5 alongside imported strains. Tunisia's Omicron wave was mainly driven by BA.2 and its recombinants, with evidence of localized viral evolution and sporadic introductions. The detection of rare recombinants underlines the importance of integrating regional genomic surveillance with epidemiological data in order to help guide future public health strategies.