Supervisors info:
Δημήτριος Παρασκευής, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Ευαγγελία Γεωργία Κωστάκη, Βιοστατιστικός PhD, Ιατρική Σχολή, ΕΚΠΑ
Μαγδαληνή Μπλέτσα, Ιολόγος-Μοριακή Επιδημιολόγος PhD, Ιατρική Σχολή, ΕΚΠΑ
Summary:
Background: SARS-CoV-2 is an RNA virus prone to mutations, which can result in the emergence of variants. As of January 2024, five variants of concern (VOCs) have been reported: Alpha, Beta, Gamma, Delta, and Omicron. First detected in November 2021, Omicron has become the dominant variant globally. This variant has produced many lineages, with new ones continuing to emerge and spread. This study investigates the spread and characteristics of four notable subvariants of the Omicron variant of SARS-CoV-2: BA.2.75*, XBB.1.5*, EG.5*, and BA.2.86*, selected due to their significant impact on transmission rates, vaccine escape, and clinical severity, aiming to provide a comprehensive understanding of their epidemiological impact.
Methods: We analyzed the prevalence, circulation dynamics, and dispersal patterns of the selected subvariants using open access SARS-CoV-2 data from the GISAID database. The research utilized the CoV-Spectrum platform and the outbreak.info tool to derive proportions of cases and insights into the spread and characteristics of the subvariants.
Results: The analysis indicates distinct dispersal patterns among the subvariants, with an inverse relationship observed between BA.2.75* and XBB.1.5*, as well as between XBB.1.5* and EG.5*, suggesting competitive displacement dynamics. The contrasting prevalence rates of EG.5* and BA.2.86* across continents, especially in Africa, and the dominance maintenance of XBB.1.5* in South America, suggest regional variations in subvariant dominance. Further examination highlights the prolonged circulation of BA.2.75*, potentially attributed to selective advantages of its sublineages. Moreover, the rapid rise of XBB.1.5* subsequent to its introduction during the Christmas and New Year period, followed by a decline post-vaccine rollout, signifies the efficacy of vaccination initiatives. Meanwhile, EG.5* exhibited a notable surge in the northern hemisphere during the summer of 2023, likely due to increased mobility, and BA.2.86* exhibited exponential growth towards the end of 2023, raising concerns due to its mutations and immune evasion capabilities. In Europe, the circulation dynamics of the subvariants closely mirrored global trends, with notable fluctuations influenced by travel patterns, especially in high-tourism regions like Portugal or Greece during the summer months.
Conclusion: These findings reveal the temporal and geographical trends in the emergence and spread of the selected subvariants, highlighting the importance of continuous genomic surveillance and adaptive public health strategies to manage the evolving landscape of SARS-CoV-2 variants. The study also underscores the challenges in this area, including sampling biases, sequencing delays, and infrastructural disparities, particularly in Africa.
Keywords:
SARS-CoV-2, Omicron, VOC, Subvariants, Epidemiology
