Molecular Investigation of Dengue Virus Serotypes in the Dengue Outbreak of 2022 in Nepal.

Background Dengue, a viral infection highly prevalent in tropical regions, exhibits local variations in risks that are influenced by a combination of climatic, socioeconomic, and environmental factors. It is caused by four distinct, yet closely related serotypes of the dengue virus. Objective 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. Method Serum samples from suspected dengue patients visiting Dhulikhel Hospital were analyzed using Dengue Rapid Test, for the presence of IgG/IgM antibodies or NS1 Ag. The positive samples were stored at -80⁰C, and 89 samples were selected for further analysis. RNA was extracted from those positive samples and RT-PCR was performed to identify the serotypes present. Result 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. RT-PCR, of 53 out of 89 serologically positive samples, by RT-PCR revealed that DENV1 was the predominant, 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 slightly higher 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.