Dengue Virus Serotype 2 Cosmopolitan C Genotype Reemerges With a New Strain in Southwest Region of Bangladesh

In 2023, the dengue virus (DENV) outbreak infected over 0.3 million cases and 1500 deaths in Bangladesh. Our study conducted serotyping and genomic surveillance in four districts of Southwest Bangladesh between September and October 2023. The surveillance data from 2019 to 2023 extracted from the Directorate General of Health Services in Bangladesh indicated a significant increase of Dengue infections in 2023, particularly during September–November. The two-layered hypothesis examination confirmed that, despite endemic months, 2023 dengue outbreak had a higher morbidity rate compared to previous years (2019–2022) in the southwest of Bangladesh. Serotyping using RT-PCR and E gene sequence analysis of 25 randomly selected positive samples reveals that DENV-2 was the dominant serotype circulating in this region during the study period. Genomic analysis (phylogenetic analysis and classical multidimensional scaling [cMDS]) exposed a new strain of DENV-2, classified under Cosmopolitan genotype within C clade, distinct from previous Bangladeshi strains until 2022. This strain, possibly migrating from India, might have emerged during the COVID-19 pandemic years and exhibited higher morbidity rates, thus challenging our existing mitigation strategies. This investigation provides valuable insights for public health interventions and underscores the importance of continuous genomic surveillance in managing dengue outbreaks.