Resurgence of Dengue Virus Serotype 2: Findings from the 2023 Bangladesh Outbreak.

Bangladesh experienced the largest and deadliest dengue outbreak in 2023, after the virus had reappeared in the country 2 decades earlier. A total of 1,705 people died in Bangladesh, representing the highest case fatality rate (0.5%) due to dengue in the world for that year. The severity of dengue infection is to some extent related to the emergence of new circulating serotypes. To identify the possible predominant serotype in 2023, the reverse transcription polymerase chain reaction-based identification technique was used on stored serum samples of suspected dengue patients during the period between July and December 2023. The overall result of molecular serotyping showed that dengue virus (DENV-2) reappeared as the predominant serotype (74.1%), followed by a moderate number of samples with DENV-1 (19.8%) and DENV-3 (6.1%), in 2023. However, DENV-1 was found to be dominant in a few rural areas of Cox's Bazar districts. During the 2019 outbreak, DENV-3 was the dominant serotype, which seemed to be replaced by the DENV-2 serotype; this may have impacted the increased case fatality in 2023.