Molecular Investigation of DENV serotypes in the dengue outbreak of 2022 in Nepal

Introduction Dengue, a viral infection highly prevalent in tropical regions, exhibits local variations in risk that are influenced by a combination of climatic, socioeconomic, and environmental factors. The disease is caused by four distinct yet closely related serotypes of the dengue virus: DENV-1, DENV-2, DENV-3, and DENV-4. Objectives The objective of this study is to identify the different serotypes of dengue virus responsible for the 2022 outbreak in Nepal, where dengue has been prevalent since 2006 but with limited availability of molecular information on the serotypes. Methodology Serum samples from suspected dengue patients visiting Dhulikhel Hospital were analyzed using Dengue Ag and IgM/IgG Ab Kit test, for the presence of IgG/IgM antibodies or NS1 Ag. The positive samples were stored at -80 °C, and 89 samples were selected for further analysis. RNA was extracted from those positive samples using the Zymo Quick RNA Viral Kit, and RT-PCR was performed using the Sacace Dengue Real Genotype qPCR kit to identify the dengue virus serotypes present. Results The study included 89 samples, of which a higher percentage of sero-positivity was observed in females (52%) compared to males. Positive cases were distributed in 14 different districts, with the highest percentage (58.4%) in Kavre. Molecular investigation, of 53 out of 89 serologically positive samples, by qPCR revealed that DENV1 was the predominant serotype, followed by DEN3 (24.5%) and DENV2 (16.9%). DENV4 was not detected in any of the samples. The average Ct value of all serotypes was 17.6, with DENV3 having the lowest Ct value of 16.6, indicating a high viremia. Conclusion Our study, although limited in its coverage of Nepal, has provided molecular information on the serotypes responsible for the 2022 dengue outbreak. The high prevalence of DENV1 was observed, while prevalence of DENV3 was accompanied by high viral load. This information provided valuable insight into the circulating serotypes of the virus in the region.